If you only need to differentiate between :10 and :50, just use ROUND instead
of ROUNDUP.
To address the initial question, where anything under :15 rounds down and
anything :15 or over rounds up, you can still use round, but add a few
minutes to bias the rounding. In particular, :15 is 1/4 hour; rounding
normally goes up beginning with 1/2. So you need to add (1/2 - 1/4) to the
elapsed hours:
=round(((c28-b28)*24)+1/4,0)

"Siteman" wrote:

I am using this formula to rond up times, in order to caclculate

=ROUNDUP((C28-B28)*24,0)

the only thing is sometimes it is best to rounddown,

for example, numbers under a quarter hour should go down, an numbers, or
times over a quarter hour should go up

If i only want to do the follwoing is there a formula for this

3:50 = 4:00
3:10 = 3:00
any number ending with :10 round down
any numaber ending with :50 round up?