Whether or not shipping should be taxed
Sets the currency for the cart. The default currency is USD. You do not need to call this unless you are using a different currency
Allows the user to specify a base XML file or string that will be used instead of generating the entire string. The user can then add items to this XML using the addItem method.
Sets the mode of the operation to use either the sandbox or live Google Checkout site. You only need to call this if using the sandbox as the class defaults to using the live site.
Adds a general shipping rule. You may add multiple rules of which the user may choose one
Sets a tax rate for a given state