Can you show your math formula? I’m guessing that it has some decimals beyond 2 decimal places, so the end calculation is negative or positive (ex. -0.00001 or 0.00001) which rounds as -0.00 or 0.00 based on the precision you have set. This may be affecting your condition as well, as it’s most likely looking at the underlying calculated value instead of the value shown with the precision set.
I always think of the precision and unit settings on numeric columns (as well as date formatting settings on date columns) as filters that determine how to display the value to the user. Those settings don’t ultimately affect what the final underlying value is. The underlying value is kept so you can still use the value for other calculations. Just like if you were to put a random word as the Unit value, instead of the Euro symbol, You can still work with that number as a number, otherwise any other math on that column wouldn’t work because there would be this random word breaking the math.
In your case, I would take your calculated value, multiply it by 100, round it, then divide by 100. Like this:
ROUND((76,03+70-146-0,03)*100)/100
That should give you a true rounded zero value if the result should be zero.