Need a shopping cart solution for a completed website that accurately calculates shipping costs based upon total package weight (lbs) using the shipping method the customer chooses, USPS Express Mail or USPS Priority Mail. Individual products available for purchase weigh between 1/4 lb and 2 3/4 lbs.
For Example: product X weighs 1/4lb, product Y weighs 1 lb and product Z weighs 1/2 lb
My Shopping Cart contains 6 of Product X, 3 of Product Y and 1 of Product Z for Total weight = 5 lbs
I need the shopping cart to be able to accurately calculate the total shipping cost after the customer selects either USPS Express Mail or USPS Priority Mail. USPS Shipping rates are calculated based on package weight and shipping zip codes. Postal zip code where package originates will always be 00803, this should be in the background and not revealed. The delivery zip code will vary depending on the customer's address. This shopping cart must work with the standard Paypal payment solution.