org-clock-rounding-minutes

org-clock-rounding-minutes is a variable defined in `org-clock.el'.
Its value is

0

Documentation:
Rounding minutes when clocking in or out.
The default value is 0 so that no rounding is done.
When set to a non-integer value, use the car of
`org-time-stamp-rounding-minutes', like for setting a time-stamp.

E.g. if `org-clock-rounding-minutes' is set to 5, time is 14:47
and you clock in: then the clock starts at 14:45. If you clock
out within the next 5 minutes, the clock line will be removed;
if you clock out 8 minutes after your clocked in, the clock
out time will be 14:50.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.4 of Emacs.