use strict;
use warnings;
use Math::Round;

my $test_value = 100.510;

$test_value = fp_round( $test_value, 3 );

print "$test_value\n";

sub fp_round {
	my ( $val, $places ) = @_;
	return round( $val * ( 10 ** $places ) ) / ( 10 ** $places );
}