I need to create several approvals on an Opportunity before it is marked as "Closed Won".

The approvals needed are the following -
  1. Sales Manager to approve any discounts of products
  2. Inventory Mgr to approve availability of products
  3. Finance to approve pricing & discounts of products as well.

These approvals can happen in parallel by different users belonging to the 3 different divisions - Sales, Finance, and Operations.

I tried creating multiple Approval Processes for Sales, Inventory and Finance but since they are all associated with the Opportunity object - so only 1 of the Approval process is getting triggered. Using Approval Steps make it a serial process?

Any idea how I could implement this?