@compuit It maybe worth checking exactly what round is required in your jurisdiction. In Australia the requirement is clearly stated in Tax invoices | Australian Taxation Office, an extract of which is:
- Total invoice rule – under this rule, the unrounded amounts of GST for each taxable sale should be totalled and then rounded to the nearest cent (rounding 0.5 cents upwards).
- Taxable supply rule – under this rule, you need to work out the amount of GST for each individual taxable sale. Where the unrounded amount of GST has more decimal places than your accounting system can record, the amount should be rounded up or down as appropriate. You then need to add the individual amounts and round this total to the nearest cent (rounding 0.5 cents upwards).
You and your customers don’t need to use the same rounding rules.
End Quote
Managers compliance requires interpreting “more decimal places than your accounting system can record” as Managers ability to record line item GST only to the minimum legal tender, and as a result the final rounding at the invoice level always produces no change.
Importantly for your negotiations with your supplier is the last paragraph “You and your customers don’t need to use the same rounding rules.” providing both comply with the tax offices rules.