You do not want to use floats for any part of calculating money. The larger the value the larger the error in them - not a trait you want when dealing with money. Fixed point numbers/decimals/big ints are much better for this, if you want greater than cent precision, treat the values as fractions of a cent (aka move the arbitrary decimal over one more place or however many you need for your application). The maths is the same no matter where you place the decimal point in it.