Got me a jar of American coins - mostly pennies, but nickles, dimes and quarters are there too. It's been near 2 decades since I last travelled south of the border (a little thing called HIV bigotry).
They (the coins) are generally accepted as equals (to the local currency) here, but I have chosen to segregate them. Use to be, when there was a large difference in value between the two currencies, you'd find almost only pennies but these days either currency will do. Of course, in the past half decade, I have rarely used cash, showing a decided preference for credit cards.
(now, let's analyze the various words I used for money: coins, pennies, nickles, dimes, quarters, currency(ies), cash, credit cards) hummmm
