If you’re shopping near a state border, you might be able to purchase items for a lower sales tax across state lines.

Calculating a combined sales tax rate including both state and local average tax rates, the Tax Foundation found Tennessee has the highest sales tax in the country, with a 9.45 percent rate.

Arkansas is second (9.24 percent), followed by Louisiana (8.91 percent), Washington (8.88 percent), and Alabama (8.85 percent).

Four states — Delaware New Hampshire, Montana, Oregon — don’t have sales tax. Other than those states, Alaska has the lowest rate (1.69 percent), followed by Hawaii (4.35 percent), Wisconsin (5.43 percent), Wyoming (5.49 percent), and Maine (5.50 percent).

Combined state and average local sales tax rates

The variation in sales tax is especially noticeable in more geographically compact Northeastern states, where consumers and businesses can more easily chose to shop or do business in a state with lower rates.

Delaware, for example, has signs at its borders telling drivers it is the “Home of Tax-Free Shopping.” To compete, neighboring Salem County, N.J., is exempt from the 7 percent state sales tax. “[T]his lower rate represents an implicit acknowledgement by New Jersey officials that their seven percent statewide rate is uncompetitive,” the Tax Foundation wrote.