While you can't round individual time entries on a live time tracking basis, you have the option to round them when invoicing your client.
The best way to access this feature is to navigate to Projects > select the project you're working on > select the Time tab to view any unbilled time tracking entries:
To invoice your hours, select "Invoice Unbilled Hours":
This will open a modal asking if you'd like to add your unbilled hours to the invoice. To do so, select 'Add My Hours'.
In the invoice modal, you can choose to round your hours to the nearest minute, 15 minutes, 30 minutes, or hour. Rounded invoice amounts can help make your timesheets look cleaner to clients.
Please note: rounding only affects the timesheet entries on the invoice. The original tracked time will remain the same on your Time Tracking dashboard.