Nobody gives a hoot about 0.000001 cents. Round to the nearest 1/100 cent after adding or subtracting, and you will be fine in 99.99999% of applications.

The cardinal sin isn't using doubles for currency; it's using them without understanding either the tool or the job that you're asking the tool to perform.

You've clearly never worked with accountants.

[Citation needed]

You've clearly never worked with accountants. [1]

[1] https://news.ycombinator.com/item?id=34717487

I don't know what I expected

I've been using doubles for currency knowing full well that i probably shouldn't. for 8 years now. so far I've only noticed being off by a cent here and there. yep.. just don't care. will cost more than a penny to fix it now.

Depends what you're doing with them. A value at risk calculation gives you a currency-dimensioned result that's hard to represent exactly, for example.

Yes, a more precise statement is "exact currency amounts form a group under addition" - once you depart from group operations (e.g. multiplication by non-integral scalars) you can start to consider floats.