Too many dp in amount fields

[tc847]

I find it very useful to be able to add fuel price to 3 decimal places allowing me to add a price per gallon of £1.429. But it is very strange that the calculated amount also has 3 decimal places (£76.452) since I am unable to pay with that much accuracy. I am not aware of any currencies that allow payment to 3 decimal places. And for some currencies only 0 should be allowed (there are no cents in a Yen for example).