If different brands of the same consumer commodity are expressed in more than one measuring unit, the sales agency, if it is possible to do so, shall unit price the items consistently within the same product category. The more familiar measuring unit found in the product group is to be used if conversion and uniformity are possible. When metric units appear on the consumer commodity, in addition to the other units of measure, the sales agency may use both units of measure on any stamps, tags, labels, signs, or lists.