Nearly half of all U.S. states now designate a few days in late summer where school-related items can be purchased free of sales tax. Clothing and shoes under a certain dollar amount are usually included in the list of eligible items to help parents save on back-to-school costs. Some states allow tax-free purchases of school supplies as well. Hoping to lure in value-conscious consumers, a few stores also offer special sales events on tax-free weekends.

"You actually see some of them bringing in items and doing specialty buys," Marino says. "It's like another Christmas shopping season, almost."

To avoid the crush of shoppers that descend on stores during tax holidays, Marino advises going early on the first day, or even selecting your items the day before the event and having them held. "There are a lot of stores that will allow you to pre-shop and put (clothes) aside for one or two days," he says.

If you're unsure whether your state has a sales-tax holiday, check the website of your state's department of revenue. If one doesn't exist, consider driving to a nearby state to participate in theirs if possible.