When I stop for gas, generally in Geneva, I do a hard pull, down the on-ramp, provided there isn't traffic in the vicinity. I hit 110 on the way home. The Batmobile was screamin! I get back down to the limit shortly so I don't piss off anyone.
I haven't been stopped in Michigan so idk. In some counties, people are doing 15 over on the interstate. But mostly it seems like you said, 5 and 10, city and highway...though if I'm alone on the road, I'm sticking to 6 over.
My boss at work got a ticket on the Turnpike for 5 over, a couple years ago. He said the cop asked him how fast he was going, so he replied "70" (in a 65), he already had the ticket written out, said "good, at least you know it" handed him the ticket, got back in his car and sped off. The first ticket my boss has ever had.