Tax rounding is done at ticket level so over many tickets it is not exact like calculating on total of all tickets.
Our post epos account accommodates this, usually see a tax variance of between 0.10 and 0.80 on daily sales between 2000-6000.
More smaller tickets would cause larger difference than small qty of larger tickets as more rounding on many tickets.
This is a natural occurrence and is to be expected
I took references to your databases out of public forum. If we ask for them via pm you can provide it but you should not put your database backups in public.
Increase your DB decimal places for greater accuracy.
That said, you can’t simply take round values of individual items and add them together, they won’t equal the same as the total because of the rounding (2 decimals by default).
You would need to take item values at 6+ decimal places and add them up and calculate tax, then do the same when you look at the total, take 6 decimals there and calculate tax. Your numbers will be closer to matching, but probably always a variance, until you round down to 2 decimals again ;).
I don’t know why you want to do that. You will end up with report that not match with other reports.
I think tax agency understand this rounding thing. It always and impossible that tax will be exact percentage. Imagine a coffee shop selling a few dollars per receipt, it will have a lot of rounding.
Unless you have 6 digits as Q suggested but only round it on the receipt but then if you add the paper receipt then total will not be exact match.