I had a three-digit amount of gold, something like 500 or more. I wanted to sacrifice 100 gold pieces. As soon as I had typed the second "0", the game went ahead and made the sacrifice. Same thing happened when I sacrificed 299 gp: as soon as I had typed the third digit, 9, the 299 gp were gone.

The game should wait for me to press enter before accepting the numerical input. That way you have a chance to review your offer and spot typos you've made.