Any suggestions on how to round up a decimal to the next quarter hour?

Time IN=A
Time OUT=B
ACTUAL TIME =C
ACT.TIME to DECIMAL=D
ROUND Up to quarter hour (in decimal)=E

A is formated as h:mm AM/PM
B is formated as h:mm AM/PM
C is formula +B1-A1; formated as hh.mm
D is formula =INT(I18*24)+MOD(I18*24,1)*60/100

I have tried the following for E:
=ROUNDUP(d1/0.25,0)*0.25

but where D is 0.20 E = .25 I would like 20 muniutes to round up to .50 hour

Or if D is
from 0.00 to 15.0 minutes then E = .25
from 16.0 to 30.0 minutes then E = .50
from 31.0 to 45.0 minutes the E = .75
from 46.0 to 60.0 minutes the E = 1.0


Thanks