Hi,
You needs two tax codes!
You PO contains 2 line items, so create 1st line item with a tax code(S1) of 5% non-credit tax and 2nd line item with another tax code(S2) of 12.36% non-credit service tax.
Both tax code S1 and S2 should have created with service tax condition with different tax percentage 5% and 13.62 % respectively where the same service tax condition type should assigned to NVV key in your tax procedure.
Regards,
Biju K