named: [salestax cart=cartname* noformat=1*]
old: [salestax cart* noformat*]
mandatory: NONE
optional: cart noformat
Expands into the sales tax on the subtotal of all the items ordered so far
for the cart, default cart is main. If there is no key field to derive the proper percentage, such as state
or zip code, it is set to 0. If the noformat tag is present and non-zero,
the raw number with no currency formatting will be given.