funny, same thing happened to me once with some hillbilly ass redneck... hes like i gave u a 20, u gave me a 10, i was st8 up yellin at dude and told him i wasnt opening the register.. my boss was just laughing. im like open this shit so this fool can see hes stupid... and sure enough there was NO 20s in the register... dude got hella heated almost in tears