If it is a different discount for the different categories, sure, you could do that.
but if you want to apply the same discount to multiple categories, you would use the strategy initially suggested.
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.