In the german rules it says any time during your turn, but there's no "turns", just "moves" (when you pick a die) and "rounds" (when someone rolls a die). So, when are you able to do it?A new round begins when the Startplayer roll the dice. Then each player takes his turn - selecting a die and performing his action - in player order until all dice have been used or verybody has passed.
Every time a player selects a die, and until he has finished his action, he may play any number of cards. Also during his turn, before, after or between playing cards, the player may sell his treasures.
Also, I don't understand the concept of treasure chest - why do you put the money during the game? Isn't it ok to just put all the money you have on the end?
If you do it at the end will we have a much better idea of how much you have contributed. When you do it in small uncertain amounts during the game, is it much harder to keep track of.