BrownTilly,
The rules for when you get straight time and when you get time-and-one-half are spelled out in your regional Supplement. They may differ from area to area.
Here in New England you get time-and-one-half after 5 hours if all the work is on your regular shift.
You get 8 hours straight time if you are scheduled to work 8 hours, or if during your shift, you agree to work on another shift after yours is over.
You probably would not have the "option" of intentionally punching out at 7:59 just to trigger the time-and-one-half-after-five-hours rule.