Here’s an interesting memorization idea from Reddit:
Require cashiers to memorize at least one major event from each year in history. When a customer's order is under $20, the cashier could educate them with an event that happened in that year. (self.CrazyIdeas)
“Your total is $18.15, which happens to be the year of the Battle of Waterloo. Napoleon and France were defeated by British forces under Wellington and Prussian troops under Blucher.”
The trick could be done as a customer when receiving change too.
I’ve started a wiki page with some major events if anyone wants to add events: