The Bundle Rate Shipping plugin was created to allow Jigoshop users to offer special bundle shipping rates when customers buy multiple products. The shipping rates can be set according to the shipping destination or products’ categories.
The plugin also allows you to create layers for every category, i.e. you can charge 5$ for an individual item, 3$ for an additional item bought, 2$ for the third and fourth, and nothing for every next item. The number of layers is not limited so you can set them in whichever way you want.