Here is a solution that only involves simple arithmetic:

sub roundup
{
   my $number = shift;
   my $round = shift;

   if ($number % $round) {
      return (1 + int($number/$round)) * $round;
   }
   else {
      return $number;
   }
}

while (<DATA>) {
   my ($n, $r) = split;
   print "Nunber = $n   Rounding = $r    Roundup = ", roundup( $n, $r)
+, "\n";
}

__DATA__
7 10
23 10
112 10
1325 100
1500 100
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