Seller Central Orders and ScanPower Sales do not match exactly. Users should be able to reconcile the discrepancies.
The Seller Central Sales Dashboard data for 'Ordered Product Sales' = Sum(ItemPrice*Qty Ordered). Item Price includes the principal amount of the item ordered + shipping and gift wrap credits + sales tax collected. Seller Central also reports any returns in a separate report and I do not believe they are deducted from Ordered Product Sales.
In ScanPower, the Dashboard graph only includes the principal amount of the ordered products. Sales tax and shipping/gift wrap credits are broken out in the Settlement Report section of the Dashboard; users need to add the three numbers to total Seller Central Product Sales. In the ScanPower Sales Report, Sales = the principal amount of the items ordered + any returns are deducted from the sales. Additionally, sales tax is called out separately and the shipping/gift wrap credits are included in fees section (credits offset the debit, fee, for these services). There may also be a lag for receipt of the current Settlement Report.