After Activation of the Promotional Purchase Price (PA00) , if you use a unit of measure that is not an even number, SAP seems to break the default order unit of measure (CASE 12 ) to EACHES, and divides the price between the EACH units. In the case of 24$ for a case of 12 units, it divides equally and the purchase order condition PA00 = $2 EA = $24 case. However if you case is 13 ?? It rounds down to the each and the round back up on PA00 purchase does not = $24.
Can you force promotions to create the PA00 with the default unit of measure for the article purchase ??