RE: Integration So From POS To Netsuite
you can use custom price to add different price than the base price in netsuite.
it depends on promotion type such as line item or couponing entire thing. if it is just for historical record you could apply discount for total amount of and set to certain GL account. The thing to be leary of is sale stax calculations and making sure both are handling promotion taxing the same depending on your taxing software