BIlling time per 15 minutes

BIlling time per 15 minutes

Hi all,

We use Zoho Desk for logging tickets from customers. We normally bill our customers per 15 minute slots. So if a customer logs a ticket and we solve in in, let's say, 9 minutes, we bill 15 minutes. If we solve a ticket in 23 minutes, we bill 30 minutes and so on.

We use Zoho Desk reports to create a monthly report with ticket times. But unfortunately this is the actual ticket time and not per 15 minutes. 

Is there any way with custom functions to create a report per customer with the actual ticket and the calculated ticket time per 15 minutes rounded up?

Thanks,
Marvin