diff --git a/.phase12-state.json b/.phase12-state.json
index 4b0d1eb..d170731 100644
--- a/.phase12-state.json
+++ b/.phase12-state.json
@@ -1,5 +1,8 @@
 {
   "completed_features": [],
-  "current_feature": "invoicing-stub",
-  "started_at": "2026-05-23T06:33:48.406343"
+  "current_feature": "time-rounding-rules",
+  "started_at": "2026-05-23T06:33:48.406343",
+  "attempted_features": [
+    "invoicing-stub"
+  ]
 }
\ No newline at end of file
diff --git a/GENERATION_LOG.md b/GENERATION_LOG.md
index d59bb34..0622fef 100644
--- a/GENERATION_LOG.md
+++ b/GENERATION_LOG.md
@@ -1459,3 +1459,22 @@ src/index.ts(27,25): error TS2769: No overload matches this call.
   Overload 2 of 3, '(plugin: FastifyPluginAsync<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
     Argument of type 'Promise<FastifyMultipartPlugin>' is not assignable to parameter of type 'FastifyPluginAsync<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>'.
       Type 'Promise<FastifyMultipartPlugin>' provides no match for the signature '(instance: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTy
+- `06:35:10` **INFO**   Committed feature invoicing-stub
+- `06:35:10` **INFO**   Pushed: rc=0
+
+## Phase-3 Feature: time-rounding-rules (2026-05-23 06:35:10)
+
+- `06:35:10` **INFO** Description: Settings-Option: Rundung für Time-Entries (5/15/30 min)
+- `06:35:10` **INFO**   Generating apps/api/src/db/schema.ts (ERWEITERT — füge `roundingMinutes: integer('rounding_minutes').notNull…)
+- `06:35:40` **INFO**     wrote 3445 chars in 29.4s (attempt 1)
+- `06:35:40` **INFO**   Generating apps/web/src/pages/Settings.tsx (ERWEITERT — füge Select-Field 'Time-Rounding: keine / 5min / 15min / 3…)
+- `06:36:27` **INFO**     wrote 5786 chars in 47.5s (attempt 1)
+- `06:36:27` **INFO** Running tsc --noEmit on api…
+- `06:36:29` **WARN**   tsc errors:
+src/index.ts(27,25): error TS2769: No overload matches this call.
+  Overload 1 of 3, '(plugin: FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
+    Argument of type 'Promise<FastifyMultipartPlugin>' is not assignable to parameter of type 'FastifyPluginCallback<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>'.
+      Type 'Promise<FastifyMultipartPlugin>' provides no match for the signature '(instance: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTypeProvider>, opts: { ...; }, done: (err?: Error | undefined) => void): void'.
+  Overload 2 of 3, '(plugin: FastifyPluginAsync<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>, opts?: FastifyRegisterOptions<...> | undefined): FastifyInstance<...> & PromiseLike<...>', gave the following error.
+    Argument of type 'Promise<FastifyMultipartPlugin>' is not assignable to parameter of type 'FastifyPluginAsync<{ limits: { fileSize: number; }; }, RawServerDefault, FastifyTypeProvider, FastifyBaseLogger>'.
+      Type 'Promise<FastifyMultipartPlugin>' provides no match for the signature '(instance: FastifyInstance<RawServerDefault, IncomingMessage, ServerResponse<IncomingMessage>, FastifyBaseLogger, FastifyTy
diff --git a/apps/api/src/db/schema.ts b/apps/api/src/db/schema.ts
index 7cced23..242461e 100644
--- a/apps/api/src/db/schema.ts
+++ b/apps/api/src/db/schema.ts
@@ -55,6 +55,7 @@ export const appSettings = pgTable("app_settings", {
   workspaceName: text("workspace_name").notNull().default("EmberClone"),
   defaultBillable: boolean("default_billable").notNull().default(true),
   weekStart: integer("week_start").notNull().default(1),
+  roundingMinutes: integer("rounding_minutes").notNull().default(0),
   updatedAt: timestamp("updated_at").notNull().defaultNow()
 })
 
diff --git a/apps/web/src/pages/Settings.tsx b/apps/web/src/pages/Settings.tsx
index c387d8e..92bcd85 100644
--- a/apps/web/src/pages/Settings.tsx
+++ b/apps/web/src/pages/Settings.tsx
@@ -8,6 +8,7 @@ export default function Settings() {
   const [workspaceName, setWorkspaceName] = useState('');
   const [defaultBillable, setDefaultBillable] = useState(false);
   const [weekStart, setWeekStart] = useState('Monday');
+  const [timeRounding, setTimeRounding] = useState('0');
 
   const { data: settings, isLoading, refetch } = useQuery({
     queryKey: ['settings'],
@@ -20,7 +21,12 @@ export default function Settings() {
   });
 
   const updateMutation = useMutation({
-    mutationFn: async (data: { workspaceName: string; defaultBillable: boolean; weekStart: string }) => {
+    mutationFn: async (data: { 
+      workspaceName: string; 
+      defaultBillable: boolean; 
+      weekStart: string; 
+      timeRounding: number 
+    }) => {
       return api.updateSettings(data);
     },
     onSuccess: async () => {
@@ -37,6 +43,7 @@ export default function Settings() {
       setWorkspaceName(settings.workspaceName || '');
       setDefaultBillable(settings.defaultBillable ?? false);
       setWeekStart(settings.weekStart || 'Monday');
+      setTimeRounding((settings.timeRounding ?? 0).toString());
     }
   }, [settings]);
 
@@ -46,6 +53,7 @@ export default function Settings() {
       workspaceName,
       defaultBillable,
       weekStart,
+      timeRounding: parseInt(timeRounding, 10),
     });
   };
 
@@ -113,6 +121,21 @@ export default function Settings() {
                 <option value="Sunday">Sonntag</option>
               </select>
             </div>
+
+            {/* Time Rounding */}
+            <div className="space-y-2">
+              <label className="text-sm font-medium text-slate-700">Zeiterfassung-Rundung</label>
+              <select
+                value={timeRounding}
+                onChange={(e) => setTimeRounding(e.target.value)}
+                className="w-full px-3 py-2 border border-slate-300 rounded-md focus:outline-none focus:ring-2 focus:ring-blue-500 transition-all bg-white"
+              >
+                <option value="0">Keine Rundung</option>
+                <option value="5">5 Minuten</option>
+                <option value="15">15 Minuten</option>
+                <option value="30">30 Minuten</option>
+              </select>
+            </div>
           </div>
 
           <div className="pt-4 flex justify-end">