Perhaps bizarrely, tadman's code doesn't work with all numbers. I think it's internal rounding errors on Perl's part rather than a fault with the code (though I could be wrong :). I've broken down the code to analyse what's going on, viz:

$number = 12650 / 10000;
$dp = 2;

print "Actual: $number\n";

my $exp = 10 ** $dp;

$val1 = $number * $exp;
$val2 = $val1 + 0.5;
$val3 = int($val2);
$val4 = $val3 / $exp;

print "val1 = value x exp = $val1\n";
print "val2 = val1 + 0.5 = $val2\n";
print "val3 = int(val2) = $val3\n";
print "val4 = val3 / exp = $val4\n";
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The output:

Actual: 1.265
val1 = value x exp = 126.5
val2 = val1 + 0.5 = 127
val3 = int(val2) = 126
val4 = val3 / exp = 1.26
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Verified on Win32 with ActivePerl 5.8.1 b807, and in Linux with Perl 5.8.0.

Replace the first line with "$number = 1.265;", however, and you get the correct result. Weird.