I'm a bit confused by your question, but if you want to round by time, say the nearest 15 minute interval per hour, the formula is below:

=ROUND(SUM(A2:A99)*96,0)/96

There are 96 quarter-hours in a day. Multiplying the total time by 96, rounding, and then dividing by 96 will give you the nearest quarter hour. If you want 30 min intervals, it would be 24, and so on, etc.

Do you have a sample file?

=ROUND(SUM(A2:A99)*96,0)/9

There are 96 quarter-hours in a day. Multiplying the total time by 96, rounding, and then dividing by 96 will give you the nearest quarter hour. If you want 30 min intervals, it would be 24, and so on, etc.

Do you have a sample file?