To my knowledge, whenever the kingdom needed money it collected taxes, but if the kingdom wanted extra money for wars, it collected in the form of donations. Like the one mentioned by Mr. Sarang. The Religion fund was diverted to construct dams, etc.
In a book written some 150 years ago, mentions that the prohits who collected money for performing yagas donated the money to construct the riverbed, which was overflowing during winter. On those days Brahmins never use to keep a piece of gold at their house. I will tell you name of the book soon. It was written by a christian missionary I hope