fix: handle negative-zero and half-cent rounding in formatGermanAmount

myteamwallet_backend/src/cashbox-export/cashbox-export.utils.spec.ts

@@ -133,4 +133,26 @@ describe('buildCsv', () => {
       'Datum;Typ;Wer;Notiz;Betrag;Periodensaldo\r\nKeine Buchungen im gewählten Zeitraum',
     );
   });
+
+  it('formats negative-zero as positive zero', () => {
+    const csv = buildCsv([
+      { date: '2026-08-05T00:00:00.000Z', type: 'expense', who: 'Teamkasse', note: 'Test', amount: -0.001, runningTotal: 0 },
+    ]);
+
+    expect(csv).toBe(
+      'Datum;Typ;Wer;Notiz;Betrag;Periodensaldo\r\n' +
+        '2026-08-05;Ausgabe;Teamkasse;Test;0,00;0,00',
+    );
+  });
+
+  it('rounds half-cent boundaries correctly', () => {
+    const csv = buildCsv([
+      { date: '2026-08-05T00:00:00.000Z', type: 'payment', who: 'Alex Muster', note: 'Test', amount: 1.005, runningTotal: 1.005 },
+    ]);
+
+    expect(csv).toBe(
+      'Datum;Typ;Wer;Notiz;Betrag;Periodensaldo\r\n' +
+        '2026-08-05;Zahlung;Alex Muster;Test;1,01;1,01',
+    );
+  });
 });

myteamwallet_backend/src/cashbox-export/cashbox-export.utils.ts

@@ -68,7 +68,9 @@ const TYPE_LABELS: Record<string, string> = {
 };
 
 function formatGermanAmount(value: number): string {
-  return value.toFixed(2).replace('.', ',');
+  const rounded = Math.round((value + Number.EPSILON) * 100) / 100;
+  const normalized = rounded === 0 ? 0 : rounded;
+  return normalized.toFixed(2).replace('.', ',');
 }
 
 function escapeCsvField(value: string): string {