Floating point values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly 
printing it without any mathematical operations.

If you would like to know more about "floats" and what IEEE
754 is, read this:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
 
Thank you for your interest in PHP.

The result of 21.33*1.015 is stored as slightly less than 21.64995 (21.649949999999997 on my Windows system), different than when you write the literal static value. The result of 21.33*1.015 when printing it (happens differently than round() function, so results may vary) or rounding 5-14 decimal places, those extra internal 9s are "rolled over."

Cool,  but this is still an inconsistency.  Any string value of the number is treated is differently then when passed to round().   This is still a very serious problem for us because we are storing all of this information in a SQL database,  the number will be lost when we build the query. 

I think you'll tell me that you don't care if people loose money when they use your platform and that you'll tell me to use someone Else's code,  like BC Math.   I think that relying on 3rd party extensions to fix your mistakes is unprofessional.

Peace

It's the CPU which is "broken", read the link provided.