diff --git a/src/lib/timer.tsx b/src/lib/timer.tsx
index d2e2ecf..210e0db 100644
--- a/src/lib/timer.tsx
+++ b/src/lib/timer.tsx
@@ -184,3 +184,10 @@ export function roundToTenth(hours: number): number {
   if (!hours || hours <= 0) return 0;
   return Math.max(0.1, Math.round(Math.ceil(hours * 10)) / 10);
 }
+
+/** Round hours UP to the nearest 1/6 hour (10-minute) increment, with 1/6 minimum. */
+export function roundToSixth(hours: number): number {
+  if (!hours || hours <= 0) return 0;
+  const sixths = Math.max(1, Math.ceil(hours * 6));
+  return Math.round((sixths / 6) * 1000) / 1000;
+}