You should consult with tax professionals to determine whether your store needs to collect sales taxes or not. Taxes can be quite taxing but once you have figured out which taxes you need to collect, it's quite easy to setup SiteGUI Commerce to collect taxes for your store.

Before you can use the Tax app to calculate and collect tax for each order, it is necessary to configure it to fit your store. Click on the App Listing menu, choose Apps to list all available apps for your Site and then click on Configure for the Tax app. Firstly, you need to determine whether the prices set for your products already include tax amount (tax inclusive price) or not. If the prices are tax inclusive, you should turn on Tax Inclusive to avoid adding another tax amount to the price, the tax amount will be taken out from the price instead. In some jurisdictions, the advertised prices must include tax, in that case using tax inclusive price for products' price is more convenient.

Next, you should determine whether to charge tax on the shipping fee and whether the tax amount is rounded for each item or rounded after they are summed up. Once again, you should consult with your tax professionals to be compliant.

Click on the New menu and choose Tax to create a new Tax rate. Then specify a name and a rate for the tax rate, you should use a tax name that your customers are familiar with. This tax name and rate will be shown on the order form. Next, choose the country and state to apply the tax. If the country is empty it will be applied to all countries and if the state is empty it will be applied to all states.

You may create different tax rates for different states or regions and use tax levels to determine how the tax is calculated. The Tax app always chooses the most specific (has state specified) and the highest tax rate in each level to calculate tax, level 1 tax amount will be calculated first, then continue to add level 2 and level 3 tax amount. If the level 2 or 3 is a compound rate, the Tax app will calculate tax for not only the order amount but also the prior level tax amount (tax over prior level taxes).

Finally, determine whether this tax rate applies to the shipping fee and Enable it to make it an effective tax rate.

Multiple tax rates can be created and they can be overlapping. Click on the App Listing menu and choose Taxes to see all available rates. Rates can be edited, cloned or deleted. Active rates will be applied to all products having no tax rate set. Inactive rates can be set as the special tax rate for products (if required by the local jurisdiction).