Let's say you have a category with similar products. Each product in this category has quantity discounts (set under the Prices tab on product edit), the more you buy the cheaper the products get. But as it is they can't mix and match.

For instance, product A and B is in the same default category.

• Product A is priced as 50€ each for quantities below 5 and 40€ each for quantities 5 and above.
• Product B is priced as 30€ each for quantities below 5 and 25€ each for quantities 5 and above.

When a customer buys 3 product A and 2 product B, the products are priced at 50€ and 30€ respectively. With this module installed, they will be priced at 40€ and 25€.
You can do this for all the categories you want, the other categories will not be affected.
The module requires override files to be uploaded to your server.
The module uses the default category of the products as the category.