You can do that with math on the page.
Shipping: <?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->GetShipping()/1.2); ?>
Tax: <?php echo WA_eCart_DisplayMoney($eCart1, $eCart1->GetTax() + ((0.2*$eCart1->GetShipping())/1.2)); ?>
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.