The Collaborative International Dictionary of English v.0.48:

Pennyworth \Pen"ny*worth`\, n.
   1. A penny's worth; as much as may be bought for a penny. "A
      dear pennyworth." --Evelyn.
      [1913 Webster]

   2. Hence: The full value of one's penny expended; due return
      for money laid out; a good bargain; a bargain.
      [1913 Webster]

            The priests sold the better pennyworths. --Locke.
      [1913 Webster]

   3. A small quantity; a trifle. --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pennyworth
    n 1: the amount that can be bought for a penny [syn:
         pennyworth, penn'orth]