Please do a Google search using key words "SAP US PAYROLL" and you should be able to find many links on the subject, such as
http://wiki.sdn.sap.com/wiki/display/ERPHCM/SAP+HCM+Payroll+USA
http://help.sap.com/printdocu/core/print46c/en/data/pdf/pyus/pyus.pdf
Once you have read on the subject, I would suggest that you post your query in the SAP ERP HCM Payroll North America discussion forum (http://scn.sap.com/community/erp/hcm/payroll-north-america).