When doing online shopping it is the best practice to compare pricing in the cart into the checkout page, like this you will see all charges like shipping and tax with a final total to compare.
Most retailers already offer free shipping on most items, but it sometimes depends if you are a member or if the order total is above a certain amount of dollars.
Once you are at checkout you can also in most cases already see a shipping estimate when the products will arrive at you, this is useful information when you are in a rush to get the product quickly.
Plus you have the benefit of detecting if there is better pricing in the cart then originally published, why would that be? As already mentioned there is map enforced pricing by vendors where sometimes it doesn’t apply in the cart, you could also gain from savings that are promoted elsewhere as BOGO savings and you missed it but the 2 items in the cart qualify and the retailer is nice enough to calculate that for you.