Can I add discount on total bill?

    Yes, But you have to enable an option from configuration.
  • Go to Setup > Configuration > Inventory Setting.
  • Enable a option "Enable Bill Discount in Percentage".If you want to give discount as amount you can also enable an option
    "Enable Bill Discount as Fixed Amount".
  • Then you can see Item Discount(%) at the bottom of purchase transaction.You can enter value in percentage.
  • If you want to gives discount as amount you have to enter the value in "Item discount(Rs)".