Understanding the concept of rounding up or down is an important math skill to master. It particularly comes in handy — as my third grader learned this week — when making numerical estimations. However, when actual dollars and cents are in play, rounding up isn’t such a good thing — especially if the practice is subtly cheating consumers in the name of efficiency.

With the help of The New Jersey Star-Ledger‘s Bamboozled blog, Chipotle Mexican Grill (NYSE:CMG) customer Jayson Greenberg recently brought attention to the company’s policy of rounding a bill to the nearest nickel.

“The receipts at the Chipotle in West Caldwell don’t add up when there are odd amounts involved,” Greenberg told Bamboozled.

Greenberg proved his point by providing the blog with the following receipts he collected from various trips to the restaurant:

“On the first, dated July 13, the nine items added up to $32.93. There was $2.31 in tax. The total should have been $35.24, but next to the ‘total’ line on the receipt, it said $35.25. The next receipt, with the same sale date, showed a subtotal of $8.64. The tax was $0.60, so the grand total should have been $9.24. But no. With Chipotle-style math, the total was $9.25.”

Chipotle spokesman Chris Arnold told The New York Times that the Tex-Mex chain uses rounding in some areas of its Boston, New Jersey and New York markets.

Arnold went on to explain that the intent of the rounding was not to cheat customers, but to help keep long lines moving quickly by cutting back on the time it takes to count out pennies. While he said that the majority of Chipotle customers consider the rounding “a nonissue,” some customers, like Greenberg, have complained.

The chain still uses rounding, but it now only rounds down. It’s doubtful customers will gripe about that.