I am not seeing the logic there.
If they are going to round up dimensions you input then there is no reason for you to round up your dimensions.
I’ve had one package flagged by UPS in 26 years and I won that case as it was sent in a standardized box with known size.
If they decide to retract this policy then you many need to go back once again edit your dimensions.
I offer UPS and USPS on some listings as one is cheaper for certain zip codes and the other is cheaper for other zip codes. If eBay actually fixes their policy of rounding up dimensions for USPS, which violates USPS policy, then your package dimensions will be wrong for USPS.
Having wrong rounded up dimensions for USPS could mean paying the next highest Cubic tier rate or disqualifying the package from Cubic rates in addition to subjecting packages to dimensional rates when they should not be.
From looking at eBay’ Developer Program briefly it stated that software developers were suppose disavow decimal values. If you are using Garage Sale that could mean GS is rounding up values and submitting them per previous talk on this forum or submitting decimal values and eBay is rounding them up on the back end.
If it was up to me eBay would be given 30 days to fix its rounding fraud and FVF on shipping fraud or loose their USPS discounts.