In Japan, it's customary to use a coin locker at a train station to store your bags, so that you can spend time visiting a place without lugging all your stuff everywhere.
Unfortunately, this coin locker only takes five ¥100 coins (I've been spoiled by newer ones in Tokyo and Osaka that take IC cards like Suica) and I only had a single ¥100 coin on me.
So I went to a 7-Eleven to change a ¥1000 bill to coins and the attendant told me that they can no longer break change. So then I bought a bottle of tea in cash, but because these days you pay with cash using an automatic machine mounted in front of the register, it gave me back one ¥500 coin and three ¥100 coins. So I still only had four ¥100 coins when I needed five to use the locker.
So then I turned around and bought a donut with the ¥500 coin in order to break change again and this time I received three more ¥100 coins.
All so that I could pay ¥500 to use a coin locker… always an adventure!