#!/perl/bin -w

use strict;
use Math::Round; # Not standard with Perl delivered

my @number = qw(3 3.555 3.222334 3.4 1 0);

for my $float(@number) {
$float = nearest(.001, $float);
print "$float\n";
}

__END__

Result of Math::Round
3
3.555
3.222
3.4
1
0

This is what I want to get

3.000
3.555
3.222
3.400
1.000
0.000