You need to add the shipping charge to the price in the hidden form element where it is being passed to paypal.
It should be in one of the form elements inside the DO loop for the cart. You will see it is set to the Price column and would need to be updated to add the Shipping column to that price so that paypal will think the total is correct.
You could either do the math right there in the hidden form element, or add a calculation to the cart: PaypalPrice = [Price] + [Shipping]
Then just refer to the PaypalPrice when passing to paypal.