Our time keeping systems utilizes a 6 minute rule. If your time-in is 8:25, I want it to automatically round the total to the nearest 6 minute increment.

TIME IN: 8:25
TIME OUT: 12:00
TOTAL: 4.50

This is the current formula in the total cell:
=IF((OR(C8="",C7="")),0,IF((C8<C7),((C8-C7)*24)+24,(C8-C7)*24))

How do I modify this so it rounds to the nearest 6 minute increment?