Shipping cost staying in the SIMPLE cart

I added a simple cart in my main template of powerstore v2. And after a user orders something and it's a successful order, if they stay on the site, on the pages that utilize the main template (where I added the simple cart in the right column) - it keeps the shipping amount in the cart for whatever reason. So it shows Zero for items in the cart but under that, where it displays the Total $ amount - it displays the shipping cost for the order they just ordered. It should be empty but instead, it shows a shipping amount in their cart. It goes away if you View the cart. But until they view it, it shows that dollar amount equal to the shipping cost of the last item they ordered. How do I get rid of this.