It won’t be related to your operating system.
SambaPOS is used by thousands of businesses worldwide, so it isn’t a bug in the software. It will definitely be down to something that has been set in your settings.
You said you checked rounding was all at 0 when QMacKay asked you before. Did you check all the places where rounding could be?
I note you are using V4, I checked these on V4.
You need to check:
Settings > Program Settings > Payment Screen Settings. “Auto Rounding” should be
Products > Tax Templates. Either make sure you have no tax templates, or if you have, make sure “Rounding” is set to
Tickets > Payment Types. For each
Payment Type, check
Payment Processors, make sure you either do not have, or check
Settings for each one and make sure there is no “Rounding” set.
Tickets > Calculation Types. Make sure you don’t have any related to Rounding. Check into each one and make sure “Rounding” is set at
Unless you have added any extra automation / rules, the above are the only places you should need to check.
Also, what exactly happens - if you have a 4.20 ticket and you go to Settle, at which point is it changing to 4.00? Are you being asked for 4.20 or 4.00 payment? If it’s a different amount, please take a screenshot of your Settle screen.