Sales tax laws differ state to state. You need to check with your own state's tax code (if it's online) or with a tax attorney for guidance.

Wisconsin is one example of a state with an exemption, but it does get a little tricky. Here is how it reads:

An exemption from Wisconsin sales and use tax is created for the sale of, and the storage, use, or other consumption of, the U.S. flag and the Wisconsin state flag.

A flag, for purposes of this exemption, is considered to include the staff to which the flag is permanently mounted when sold by the retailer. However, if a flag is sold together with other tangible personal property, such as a pole to which the flag may be attached and unattached, and mounting brackets, only that portion of the selling price attributable to the flag is exempt from Wisconsin sales and use tax.