As Abigail-II says, sprintf will guarantee two digits after the decimal point. But it won't guarantee consistent rounding. Try this:

my @nums = ( 62, 63, 64, 65 );
for ( @nums ) {
   $_ += 0.005;
   printf "%.2f\n", $_;
}
[download]

Output (at least on my machine):

62.01
63.01
64.00
65.00
[download]

To quote Zaxo from the thread (s)printf and rounding woes:

"That is a general property of binary floating-point numbers... If you need consistency in a fixed-point decimal representation, you should scale the numbers to be represented as integers."

dave