sub consistentlyRound {
    my( $w ) = @_;
    my $p = int( ($w+0.005)*100 );
    return $p/100;
}

my $x = 0.015;
my $y = 0.0001;
$y += 0.0001 for 1..149;
print "x=$x y=$y\n";
printf "x~%.2f y~%.2f (stupid printf rounding)\n", $x, $y;
$x = consistentlyRound( $x );
$y = consistentlyRound( $y );
print "x~$x y~$y (consistent arithmetic rounding)\n";
__END__
x=0.015 y=0.015
x~0.01 y~0.01 (stupid printf rounding)
x~0.02 y~0.01 (consistent arithmetic rounding)