Rounding issues cannot be worked around – except by manually putting in the rounding. See How do I Activate Rounding
If you are GST exclusive, then you will get rounding issues if you are expecting the invoice total to be the sum of the product GST Inclusive values. The product that is 4.35 exclusive of GST – is not 5.00 with GST added, it is 5.0025.
It doesn’t matter if its 5 items that are all different or all the same, and priced at 4.35.
If you add up the GST exclusive values, add GST to that and round that once – Value A
or you take the GST inclusive (but rounded) values and add them up – Value B
Value A and Value B will differ.
So the pricing change/difference you see with 10.00 – is exactly the same idea. There is no rate, to 4 decimal places – that multiplied by 1.15 gives you 10.0000 exactly.
The values 8.6956 and 8.6957 and 8.6956 all differ from 10.0000 ie 9.9999(9.99994) and 10.0001 (10.000055)