convert decimal numbers to a fraction of an hour for payroll hour

need to convert payroll hours to 1/4 of an hour.

e.g 123.56 convert to 123 hrs and 45 minutes
123.78 convert to 124 hours
decimals of 0-25 = 15 minutes
26 - 50 = 30 minutes
51 - 75 = 45 minutes
76 - 99 = 60 minutes

using office 2000