I have to admit that I do a mental rounded total before I get to the cash register. Was in our Fabricland a couple of weeks ago and just about fainted when the total came to $56--and the the cashier (NOT the brightest bulb in the store--and I should have been prepared!!) said "Oh, I forgot to give you the discount"--DUH it was a 40% off sale!!
No matter what type of store I go into, I ALWAYS check my receipt before I leave.