A lot of them ...

You are going to have to manage everything on a daily basis to handle the current currency ratio and alter the prices of all of the products everyday and ensure that this is done consistantly to change the prices of all products everytime you update the currencies ...

Is this really worth the effort of tracking down all the locations for this kind of coding change vs leave it as is or pick your main currency to do this and allow the other currencies to manipulate from that?