Sales taxes include any taxes due to the sale, including, for example, VAT.

The stated license price does not include taxes due to the sale. You are responsible for any normal and typical sales, value added or use taxes imposed by the legal jurisdiction, country or state, from which you are purchasing, or in which you reside, whichever may be required by the applicable taxing authority. The Digital River shopping cart will add any applicable taxes to your cart during the ordering process. If the amount assessed by Digital River later is found to have been inadequate under the laws of your territorial jurisdiction, we reserve a right to reassess the difference.
The following references are not necessarily definitive nor binding upon DayZero or Digital River. However, for anyone wishing to learn more about the different forms of sales taxes, starting points are the following links:

Sales Taxes are as usually defined in the US.

Use Taxes are imposed by some US States where they are unable to collect sales tax at teh point of sale.

VAT or GST are normal terms, in English, for most countries outside of the US.