Sales-tax holidays don't kick off with the same fanfare as Amazon Prime Day, but saving 5% or 6% on your back-to-school shopping tab is nothing to sneeze at.

Across the country, more than a dozen states and Puerto Rico will hold these tax-free days in the next few weeks, a number that has fallen slightly since reaching a peak in 2010, when 19 states participated, according to the Tax Foundation.

Tax-free shopping is a welcome opportunity for local brick-and-mortar retailers to boost foot traffic as online retailers such as Amazon grab more and more market share.

The holidays must be approved by states legislatures and treated like any other expense. In order to balance the budget, states may have to suspend the perk or drop funding for another program.

For the tax-free days that still remain, most are held over the course of a weekend in August, although each state offers shoppers its own specific savings.

In Massachusetts, for example, purchases under $2,500, including meals, are exempt from the state's 6.25% sales tax.

In Tennessee, which has one of the highest sales tax rates in the country, at 7%, footwear or apparel that cost less than $100 are temporarily tax-free. Same for Virginia, which also eliminates sales tax on certain hurricane-preparedness products.

Maryland offers similar exemptions on clothing and shoes and provides a break on backpacks under $40. There, the tax-free holiday lasts for a full week, from Aug. 11 through Aug.17.