[BNM] php rounding bizzarreness

['Alex' Bridge]

Andy Galletly wrote:
> I'm willing to admit my maths may be dodgy at times, but,
> how come php does this?
>   
[snip]

> Surely the vat should round up, the same as the total rounds up??
>   
Looks like you're using an older version of PHP - up to version 4.2.x it 
used Banker's rounding , which on exact halves always rounds to the even 
number.

http://en.wikipedia.org/wiki/Significance_arithmetic ("The round-to-even 
rounding rule") for details of why one might want to round that way.

Cheers,

-alx