I think this would be better:

sub RoundUp
{
$float=$_[0];
...
..check that your input is valid here..
...
my $rounded_number=$float;
  if($float==int($float)){
  }elsif($float>0){
     $rounded_number=int($float+1);
###################################
## and optionally, depending how ##
## you want to define ceil() on  ##
## a number less than 0..        ##
  }elsif($float<0){
     $rounded_number=int($float-1); 
  }
###################################

return rounded_number;
}
[download]

The code above rounds any number smaller than 9e-9 incorrectly to 0. For a lot of applications I suppose this won't make a difference, but why write a mathematical function that is not correct? It might be copied by someone else who assumes that it will work correctly in every circumstance*.
*Yes it would be a stupid assumption to make, but you can never tell..
waits for someone to point out the error in her method
why_bird