Sales Tax

a tax on stuff you buy

http://en.wikipedia.org/wiki/Sales_tax

often there are different Sales Tax rates for different types of goods, to either encourage/stimulate certain types of purchases or punish/discourage others (e.g. Gas Tax, Cigarette Tax, etc.)

see also VAT

If you're doing E Commerce or running a market, you need to calculate this accurately.

• Dec'2012: A friend recommended http://exactor.com/