Floats are fine for speculation. But they should not be used to record actual transactions.
I typically use the smaller unit of a currency to store transaction amounts. E.g., for a US transaction of $10, I would store the integer 1000 because that is 1000 cents.
> The finance industry mostly uses floats for currency, up until settlement etc.
Having done some work on pensions and insurance point-of-sale illustrations & related in the 00s and very early 10s, I'd say that is not correct, at least not here in the UK. Almost everything was specified as intermediate values to 4dp (so hundredths of a penny) and rounded to 2dp for final results.
Though it wasn't consistent: one of the problems we experienced was that while actuarial departments were following this rule others modelling for themselves in Excel or using online calculators (written in JS) were not (as those are all based on IEEE double-precision floats by default, you have to scale and manage scaled ints yourself to get accurate 4dp decimal) so we'd get reports that our calcs were off compared to what the planner's workbook gave (over the length of a pension the rounding errors can compound to quite a noticeable difference).
I've not worked in that are for well over a decade now so maybe things have changed towards floats being the default, but that seems odd to my as it isn't an industry that tends to be happy with reducing precision.
"What would I get for this share?" can be answered with a float.
"What did I get for selling this share?" should probably be a fixed point value.