Sum time then round to nearest 5 minutes

Hi

not being my area of expertise this, wondered if anyone could give me a simple formula for the following:

I have a list of timings [hh]:mm
what I need to do is add 15 minutes for each elapsed hour.

E.g.

A1:07:15
A2:04:45

new time would read

B1:09:00
B2:05:45

In M5 I have 00:15 to act as the trigger for the 15 minutes

I have created this formula which seems to work fine: =SUM(A1+(HOUR(A1)*$M$5))

the next bit I can't seem to work is how to round the number up to the nearest 5 minutes.

any ideas please?

Try

=CEILING(A1+(HOUR(A1)*$M$5),"0:05:00"+0)

perfect thanks

You're welcome.