Q: When is it okay to tip in anything besides the local currency?
A: If the choice is that or nothing, then leave the non-local currency. But otherwise, try your best to leave a tip in the
currency of that country.
Run out and grab some change on your lunch
break, or visit an ATM.
By leaving a tip in a non-local currency, you're giving your service
person work to do, and they'll likely have to pay a fee to change it
into their own currency. So you should only leave a tip in your own
currency if you don't have time to get something else.
