Solution is :
For BUY 2 GET 5% - Create a shopping cart price rule, then under the Discount Amount * set your discount amount(in percentage) for eg. 5%
Under the "
Apply the rule only to cart items matching the following conditions (leave blank for all items)
"
set condition :
If ANY of these conditions are TRUE :
Quantity in cart is 2
For BUY 3 or more GET 10% - Create a shopping cart price rule, then under the Discount Amount set your discount amount(in percentage) for eg. 10%
Under the "
Apply the rule only to cart items matching the following conditions (leave blank for all items)
"
set condition :
If ANY of these conditions are TRUE :
Quantity in cart equals or greater than 3
"Quantity in cart" attribute checks the qty for same SKU.
That solved my problem.
I hope it will help someone. Thanks!