It is outright theft, at least in Illinois. I'd wager it would be in most other states as well.
720 ILCS 5/16A‑3: Offense of Retail Theft.
A person commits the offense of retail theft when he or she knowingly:
(a) Takes possession of, carries away, transfers or causes to be carried away or transferred, any merchandise displayed, held, stored or offered for sale in a retail mercantile establishment with the intention of retaining such merchandise or with the intention of depriving the merchant permanently of the possession, use or benefit of such merchandise without paying the full retail value of such merchandise