Probably because it's the lowest common denominator across all states to follow codes. https://www.nist.gov/pml/weights-and-measures/us-retail-pricing-laws-and

Probably because it's the lowest common denominator across all states to follow codes. https://www.nist.gov/pml/weights-and-measures/us-retail-pricing-laws-and-regulations-state https://www.nist.gov/pml/weights-and-measures/us-retail-pric... A company the size of Walmart would need to employ many lawyers just to deal with state to state pricing laws.