The Collaborative International Dictionary of English v.0.48:

Sixpenny \Six"pen`ny\, a.
   Of the value of, or costing, sixpence; as, a sixpenny loaf.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sixpenny
    adj 1: of trifling worth [syn: sixpenny, threepenny,
           twopenny, tuppeny, two-a-penny, twopenny-
           halfpenny]