This extension will display cart on your product page . Also will display and total price with shipping and coupon and all taxes

Check demo http://demo.plusmotiv.com/store/index.php?route=product/product&product_id=40

Add product first. If you have empty cart it will be not displayed

It can be easy modified do display shopping cart on any other page. On home page or category page.
For any suggestion write me on dal_sto@yahoo.com or in comment