I agree that treating different currency symbols as synonymous would be a good overall solution.
Or maybe the different symbols could behave the same, but different currencies gets added in as separate. So one could use them to add in different things in the same list (apart from money too, I mean). Let’s say I use euro sign for counting the money spent and dollar sign for adding up selling prices and they won’t get mixed up. That’s not mandatory however and I don’t know if that seems too complicated for other users.