Comparing within Delta

I'm doing some calculations with floats and was wondering if there is any built in functionality to do a compare equality within delta.

More or less I'm doing this

$part_one = fRequest::get('part_one', 'float');  //This can be a float, like 32.5
$part_two = fRequest::get('part_two', 'float');  //This can be a float, like 67.5

$total = $part_one + $part_two;
$delta = 0.05;

//The total must be 100%
if( (100 - $delta) < $total && $total < (100 + $delta) ) {
  //Valid value
} else {
  //Throw an exception
}

Does fNumber support anything like this? Is this necessary in PHP? I know it's normally frowned upon to write code like "if(32.5 + 67.5 == 100) {" because IEEE floating point representation isn't exact and it might add up to 99.999999999765746857999 or something crazy like that.

Thanks for any help.