To save on sales tax holidays, read the fine print

To benefit from sales tax holidays, many of which fall over this weekend, ready your shopping list. Jeans, notebooks and…disposable diapers?

Sixteen states plan to hold sales tax holidays during the month of August. Louisiana and Massachusetts usually exempt all purchases under $2,500. The rest focus on a trifecta of common back-to-school purchases: Clothing, school supplies and computers.

Read MoreWhen and where to snag sales tax breaks

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But this is one case where the fine print might provide some unexpected bonuses in a shopper's favor. State regulations dictating the terms of the holiday are often more generous than their broad overview implies. In South Carolina, for example, listed exemptions under broader category of clothing include baby diapers, costumes (for Halloween early-birds) and wedding dresses. Arkansas considers cosmetics and jewelry priced at $50 or less as exempt clothing accessories.

Of course, the fine print can still work against you. Plenty of items aren't exempt. Texas nixes athletic gear such as cleats, as well as accessories including jewelry and wallets. In some states, local taxes may also still be in effect, limiting how much shoppers save.

—By CNBC's Kelli B. Grant