Firstly I do not want to round my numbers, I am using base 10 figures so excel should have no bother doing simple add and subtract.

```
A| 665.110000000000000000000000000000
B| 4.990000000000000000000000000000
C| =a1+b1
D| 670.790000000000000000000000000000
E| 1,335.890000000000000000000000000000
F| =e1-(c1+d1)
```

I should get -5 however F1 returns

```
-4.999999999999770000000000000000
```

It is a financial document therefore I want to avoid rounding, more to the point. Why should I need to? I've put cell formatting to Currency with 2 decimal placed and I will get the correct display value but for all calculations I will still get -4.9999...7 which leads to further errors with conditional formatting etc.