#!/usr/bin/perl

use strict;
use warnings;

use POSIX;

my @data = qw( 9.90 9.91 9.9111 9.94999 9.95 9.950001 9.96 9.99 9.99999);

foreach my $x (@data) {
    printf "%s => %.2f\n", $x, floor( 20*$x) /20, "\n";
}