The idea is to allow you to modify the calculation management by first determining the net unit price and only then multiplying by the quantity. In this way, 16 rows of 1 piece would have the same value (added) as a row of 16 pieces (due to rounding).

NOW

price 221.85 , discount 49% , qty 16 the system calculate

221,85*49/100 = 108.7065

(221,85-108.7065) * 16 = 1810.2960 rounded 1810.30

DESIRED

221,85*49/100 = 108.7065 rounded 108.71

(221,85-108.71) * 16 = 1,810.24