1. A method for determining whether machine readable information on an item being scanned corresponds to said item being scanned, wherein said method comprises: a) reading said machine readable information to determine a value represented by said machine readable information; b) reading data from a data structure, wherein said data from said data structure includes a dimension of a first visible feature of a listed item corresponding to said value represented by said machine readable information, and wherein said first visible feature has a first relationship with a location of said machine readable information on said item corresponding to said value represented by said machine readable information; c) determining a dimension of a first visible feature of said item being scanned, where said first visible feature has said first relationship with a location of said machine readable information on said item being scanned; and d) comparing said dimension of said first visible feature of said item being scanned with said dimension of said first visible feature of said item corresponding to said value represented by said machine readable information.