Ohh...is there a way to override that with the paypal variable setting in Ubercart? Like having shipping=0 or shipping_x=0. I don't see that on the list of variable. I only see no_shipping which is for no shipping address, but no variable to override shipping amount:
https://www.paypal.com/IntegrationCenter/ic_std-variable-reference.html

This needs to be added to the uc_paypal.module so that if no shipping cost, then the following will be output:
<input type="hidden" name="shipping" value="0">

UPDATE: This is a hack since I don't know exactly what to put, but it works:
'shipping_1' => uc_currency_format($shipping, FALSE, FALSE, '.'),