Quantity based discounts site wide by fixed rate

I need the following discount module to give a site wide discount. The discount needs to be across a range of products based on quantities ordered.

All shoes are $10. There are 10 styles.

So if a customer buys one pair of shoes of style X they pay $10, buy any 2 pair of shoes, say style X and style Y, they pay $15 (not $20), buy any 3 pair of shoes, say style X and style Y and style G, they pay $25 (not $30).

Buy any 1 pair of shoes for $10
Buy any 2 pairs of shoes for $15
Buy any 3 pairs of shoes for $25

There are mods that add discounts at the end of the cart totals but I need to update before the cart and in the header where the price shows the total products order and total price e.g. 3 items - $30.00 - this automatically updates to show the correct price.

can anyone help please?

Try check link below:
http://www.opencartx.com/order-totals/i ... e-discount

Don't forget contact developer first to ensure that is meet what you need.