My colleague who dabbled in economics when deciding how many lunch vouchers to buy had a number of other money-related quirks.

One of the ones that I remember is that when paying for a purchase, my colleague would double the balance and give the cashier that much money. For example, if the total was \$5.20, my colleague would hand over \$10.40.

Why?

Just to see if the cashier reacted when pressing the Enter code appeared to have no effect.

Total is \$5.20.

Cash tendered is \$10.40.

Change is \$5.20.

Most of the time, the cashier wouldn't pay any attention. Heck, the cashier wouldn't even question why my colleague handed over such a strange amount of money.

Sometimes my colleague would mix it up and instead add \$6.66 to the total. For example, if the total was \$5.20, my colleague would hand over \$11.86, just to see the cashier's reaction when the cash register indicated that the change due was \$6.66.

And then one day, magic happened: The total was \$6.66. Without skipping a beat, my colleague handed over \$13.32.