# handle 5 in the thousandth's place with nothing or zeros following
$pete =~ s/(        # substitute, start capture $1
            \d*     # none or more digits
            \.      # a decimal point
            \d      # tenths digit
           (\d)     # capture hundredths digit as $2
           )        # end capture $1
           50*$     # digit 5 followed by none or more 0's to the end
          /1&$2 ? $1+.01 : $1/xe;
# then do as you had
$rooker = sprintf "%.2f", $pete;