You will have to do a manual tweak for the simple shopping cart plugin. The instruciton given above by Ivy is for the WP eStore plugin (she probably didn’t realize that you were talking about the other plugin).
Anyway, to use PayPal’s profile based shipping do the following:
Open the “wp_shopping_cart.php” file and search for the following word:
shipping_1″
once you find it then delete the whole line. save and upload and that should do it.