Where do you cash in foreign coins?

//eBay//

Correction

It very much depends on what you mean by "cash in". Normally to cash in coins or bills means to take them to a bank where you'll only get face value. If all you have are common coins, that's your best route. Many banks require large numbers of coins to be rolled and will charge a fee for counting loose ones. If you can make use of one of their gift cards, taking them to a Coinstar machine is another option. DON'T convert directly to bills; if you do that those machines will suck out 8% to 10% of what you put in.

If you mean "to sell the coins because they're collectible", then you have to know a lot more - condition, current values, etc. - if you want to sell on eBay. Alternately you could sell them to a dealer or appraiser but expect them to pay wholesale prices, maybe 1/3 less than retail, because they have to make a profit after all.