The Collaborative International Dictionary of English v.0.48:

Decimalize \Dec"i*mal*ize\, v. t.
   to convert the dominant units of measure (e.g. of currency)
   to a decimal-based system; to reduce to a decimal system; as,
   to decimalize the currency. -- Dec`i*mal*i*za"tion, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

decimalize
    v 1: change from fractions to decimals; "Stock prices will be
         decimalized in the year 2000" [syn: decimalize,
         decimalise]
    2: change to the decimal system; "The country decimalized the
       currency in 1975" [syn: decimalize, decimalise]