You'll usually be informed about that right before you confirm a transaction. Recently, just throwing btcs to a couple of exchanges, i'm being charged .0005 btc per transaction. It differs of course sometimes but that's usually the rate of transactions i'm making.
Just like what mentioned on the top comment it will be depending on how.much OP will send but since he mentioned also that $0.5 is the charge means he was only talking small amount here,and besides s OP you need nothing to add on if the transactions can be covered by the amount on your part,if the amount exceeded rhsn thats the time you need to add another amount