E-commerce customizations such as taxes and shipping must be configured through either your Google Checkout or PayPal account.
For PayPal, you can read more about what you'll need to do to set up these features here:
In Google Checkout, the settings are configured under Settings in your Google Checkout account by either clicking on Shipping Setup or Tax Setup.
https://checkout.google.com/sell/settings?section=Profile Note that the above options show how to set up flat-rate shipping. If you want to vary shipping costs from item-to-item you'll need to create custom payment buttons through PayPal instead of using our built-in e-commerce elements.