you can do by go to sales - configuration  -setting and active Coupons & Promotions-
and under product you can add promotions

Yes we agree that Setting Up the Promotion and coupon with the default price list is not the complete or accurate solution.

Here are some of the highlighting features of these apps:

Select  any of the following Promotion Levels

1) Global Discount - Applies to all products

2) Category Discount - Applies to specific product category or sub-category

3) Product Discount - Applies to specific product and all its variants

4) Variant Discount - Applies to specific product variants

Then, Select any of the following  Promotion Types

1) Fixed Price Discount

Apply flat fixed price discounts by specifying the exact amount.

2) Percentage Discount

Set specific percentage to offer flat discounts.

3) Range based Discount

Set discounts based on Price Range and Quantity Range.

4) Clubbed Promotion

Merge two promotional offers to provide additional discounts.

5) BOGO Offer

Configure Buy One Get One offer.

Other Features

• Set Promotion Duration by specifying start and end dates.

• Set overall promotion budget and specify maximum discount amount per sale.

• Auto Generate Promotion Codes or use your own code.

• Set minimum order amount or quantity of items in an order for promotion to be applicable.

• Set usage restrictions by configuring total number of times a coupon can be used and maximum number of times a customer can use a coupon.

• Configure promotions to make them available for specific customers or customer groups

• Create & Print Barcode/PDF for the Promotion

• Share Promo Code via email with customer.

• Create QR Code for the promotion and on scanning the QR Promotion will be automatically applied to your cart.   
  
  

You can create kits or bundles using BoMs to cover such functionality. Or you can look at Pragmatic's module for different promotion schemes: https://apps.openerp.com/apps/modules/9.0/pos_promotional_scheme/