This.

I generally avoid using credit cards for daily purchases, only bringing them out for big things like hotels. Any leftover currency, I use at my last hotel or two to pay down the bill before using a credit card.

I also keep some leftover currency if I intend to return. On one trip to Japan several years ago I actually made a fair amount as the exchange rate changed significantly in my favor before I returned. I wouldn't expect that to happen very often.