If my bill came out to $7.13, unless I want a .75 newspaper that I had to buy outside on the rack, I'd much rather just give the cashier $12.13 and get a $5 bill back instead of getting the loose bills and change back (I'm learning that is an interesting and sometimes frustrating concept to a 6 year old you're teaching math to LOL).
That said, I'm not that big of a dick to wait until the cashier drawer is closed, added the fact that I could end up getting a BIG blank stare if I did wait.
Perhaps that is just me though, because during my very short stint working fast food, I gave up asking people if they had extra change so I could just give them bills back. That was the nice thing about my other short stint working retail, people usually paid by credit card LOL
On a side note, don't you just HATE the people who have a bill that comes up to $10.12 and then they have the balls to take ALL 12 pennies out of the "give a penny take a penny" slush fund on the side of the register? it says "need a penny take a penny, have a penny give a penny" NOT "hey, wipe me out if you don't have enough".