Thanks @Navneeth for your response.
Answer to your questions are below.
1. No. i have not changed the sales tax code after confirmation.
2. Since answer is no on point 1, then no confirmation needed.
Below is the steps i am doing,
1. Create a PO.
2. Add financial dimensions on header.
3. Add items and add sales tax group and item sales tax group on each line details.
4. Submit workflow and once workflow is approved, confirm the PO
5. Generate product receipt on goods rec.
6. Generate Invoice and post.
From point 1 to 6, i am not able to see sales tax in totals of PO (not even in invoice total) but it is showing tax details in sales tax button on purchase order under Purchase action pane. Why it is not showing TOTAL? thats the requirement.
Regards