Sales Tax is automatically added to your orders when the settings "All Tasks->Web Site->Global Settings->Product Plugin->Include Salex Tax" is checked.
Automatically computed during checkout.
We use the same tax rates tables found on this website: http://www.taxrates.com/
Sales tax is automatically computed to your order according to the ZIP code and destination State provided. The final order review screen may display a different Sales Tax amount when the customers changes shipping information at checkout.
Sometimes, shipping charges are included too.
In some states, sales tax is also levied on shipping charges and subject to some specific rules. Our ecommerce platform keeps track of this information and will add shipping costs to the taxable amount when required.
You do not have to worry about this.
Disclaimer
If you do not currently charge sales tax, please check the regulation in your home state for best practices. LVSYS cannot be help responsible for the undercharging or overcharging of sales tax. It is your responsibility to collect and remit the proper sales tax to the proper agencies.