This online calculator will calculate the sales tax amounts and a total based on the entered tax percentages.
In the United States sales tax is assessed by most but not all states. A use tax is generally assessed on purchases made by a resident in a state that does charge a sales tax when the purchase is made from a state that does not charge a sales tax. You will generally calculate either a state or use sales tax but not both however, 2 separate fields are provided for clarity and just in-case. Local sales tax is only used if you will also charge, or pay, a tax on the local level such as to a town or municipality.
Wikipedia contributors. "Sales taxes in the United States." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 11 Apr. 2010. Web. 12 Apr. 2010.
Wikipedia contributors. "Use tax." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 24 Mar. 2010. Web. 12 Apr. 2010.