Shipping question

I want to have base shipping set for 1 product a certain price, for example $7. If the user purchases any other products in the store I want to have a lower shipping rate for those additional products, for example $3 for each additional product. So if a person orders 3 items from my store, they would pay $13 for shipping.

Is this possible with a standard WC install or do I need a plugin to do this?