Paying taxes on your purchase is a very rare case?
Anyway, yes, your main thesis right: it's entirely possible to do this with Javascript without screwing it up. But it wasn't in this one particular case.
> Paying taxes on your purchase is a very rare case?
I think the point is that the situation where floating point error changes the result when rounded to cents is rare. Which is true, except when it is not (e.g., if you happen to have a price that tickets commonly hit that results in an error.)
Anyway, yes, your main thesis right: it's entirely possible to do this with Javascript without screwing it up. But it wasn't in this one particular case.