For those of you turning in massive quantities of coins, here's a little tip to make it go faster.
First, make sure you only have coins in your inventory you want turned in. If you want to save your gold, and just turn in copper or whatever, make sure the gold coins aren't in your inventory.
Talk to the Jester. Instead of clicking on your responses, press CTRL-F1 on your keyboard. If you keep spamming CTRL-F1, you will turn in coins extremely rapidly. This will continue for many turn-ins, probably 20 or 25, and then the Jester shuts you down, and you have to talk to him again.
By the way, this works for all dialogue boxes in the game. If you want to select the first response in a list, use CTRL-F1; to choose the second response, it's CTRL-F2, etc.
Enjoy!!!