Timesheet: I'd like to restrict my time blocks duration to increments of 15 minutes (configurable)

As a timetracking freelancer, my hourly contracts often specify the time increment I will bill at. Most of them say “15 minute blocks.” Meaning, if I worked 10 minutes on something, I’d charge for 15 minutes. If i worked 35 minutes, I’d round up to 45 minutes (or down to 30 if I’m feeling generous).

I’d like the timesheet to allow me to set that option so that when I drag handles, and in the AI suggestions, it gives me durations that comply - i.e. 15 mins, 30 mins, 45 mins, 1hr 15 mins, etc.

I’d like this setting to be adjustable - for instance, I could set a project to bill at 30 minute or 1 hour increments instead.

Currently I’m manually adjusting almost every time block.