Usually this will happen automatically if the purchases are made fairly closely together.
However, are you actually asking about combined and discounted shipping?
The seller may have that set up automatically too, or may have to do it manually.
ASK THE SELLER before bidding if there is a shipping discount on multiple purchases (discount is not the same as combined) and confirm what it is.
You may have to tell the seller which items you are planning to bid on, especially if dimensional rates for shipping may be involved.
And "around $5" is not acceptable. You need a firm "$10.78 by first class international USPS" .
