no, power store does not support this sort of donation where it would not have tax applied.
tax is applied to the cart subtotal so it applies to all items in the cart.
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.