as long as you have a category column in the cart and you set it to 1 for items it should apply to and 0 for items it should not apply to, it will not affect those it should not apply to.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.