After I high school I managed a gas station for a while. Me and a buddy were working and this guy comes in and starts asking my buddy a bunch of questions about the oil (or something on that side of the store) and then this other guy comes in and bought something with a $100 and then starts asking to swap this bill for those bills, etc. It took me about 10 seconds to realize what was going on and when I was up $20 on him I closed the register and said "Have a good night". He argued with me (and now his buddy was eyeing the situation) and said I need to count the drawer I replied with "Or we could call the cops?". They left and me and my buddy enjoyed dinner on them

True story, lol.