Goto Sales->Step Discount window.
Create new discount you want to apply.

How does step discount works in Sales module

In Sales order lines, there is a column step discount displayed with list of discount created. select product and step discount you want to apply. Step discount applied before tax for product price. 
Example:
product price =288
tax = NIL
step discount=10%, 5%
Then ,
10% of product price =(288*10%) => 28.8
apply 5% discount on 288-28.8 (i.e) result= 259.2
5% of price = (259.2 *5%) => 12.96
i.e Total price = 259.2- 12.96
actual_price of product=246.24
If tax avaiable for product,then
tax=2%
tax applied for product = 246.24*2%

How does step discount works in Sales module

In Sales order lines, there is a column step discount displayed with list of discount created. select product and step discount you want to apply. Step discount applied before tax for product price. 
Example:
product price =288
tax = NIL
step discount=10%, 5%
Then ,
10% of product price =(288*10%) => 28.8
apply 5% discount on 288-28.8 (i.e) result= 259.2
5% of price = (259.2 *5%) => 12.96
i.e Total price = 259.2- 12.96
actual_price of product=246.24
If tax avaiable for product,then
tax=2%
tax applied for product = 246.24*2%

Select the Product in POS. click on step discount button near by customer button.

New Popup will displayed with list of step discount. select the discount and click OK button

Step discounts will be applied before tax calculation.

Calculation

Example:
product price =1000
tax = NIL
step discount=10%, 5%
Then ,
10% of product price =(1000*10%) => 100
step discount1=100
apply 5% discount on 1000-100 (i.e) result= 900
5% of price = 900 *5% =>45
step discount2=45
Total step discount = step discount1+step discount2
Total step discount =145
If tax avaiable for product,then
tax=2%
tax applied for product = (1000-145)*2%

POS order lines contains new column Actual price. It will display the actual price of product before discount,tax applied.