I'm sorry for not being clear enough. I have multi-currency set up in QuickBooks, and I have multiple foreign currency vendors & customers. 
My issue occurs when a foreign-currency vendor is paid in full, but because of exchange rates, it'll show up on 'Vendor Balance Summary Reports', with a home-currency balance. 

I am aware there is a way to adjust home-currency balances for foreign-currency bank accounts - is there a way to adjust home-currency balances for foreign-currency vendors?