Does anyone know a formula that will round up time to the nearest end time?

Example:

An employee's end time is 4:45 pm but the employee finished at 4:43 pm. How can i get the 4:43 pm round up to the 4:45 pm end time?

another example is:

An employee's end time is 4:45 pm but the employee finished at 4:50 pm. How can i get the 4:50 pm round up to the 4:45 pm end time?

Can anyone help me with this?

I've wrote the formula:
=IFERROR(IF(AR9="","",AR9+TIME(AR9,$F$1,0/24*24))+0.00068287037037037,"")
But what the formula does is that it rounds up but is off by a couple seconds or sometimes minutes.

If there is a formula that can give the exact end time I will be sooo happy.