How to show discount sale % on specific collections separately in LIQUID file PROGRAMATICALLY?

[AlKhaleejClinic]

I want to show price cut sale% on whole multiple collections. How can I do it PROGRAMMATICALLY?

For example:
At Collection ‘Medicine’, I want to apply 10% sale.
At Collection ‘Baby Care’, I want to apply 20% sale.
& so on.

So, All products associated with that collection will get respective sale%.

Also, it must show cut price on product price. i.e. before & after.

something like:
Rs. 2000 Rs. 2200
10% Discount

WHAT I HAVE DONE SO FAR?

{% if emphasize_price %}
{{ product_item_price }}
{% if collection.handle == "medicine" %}
Discount 10% - Save Rs. 200
{% endif %}
{% endif %}

Copy

So Far its Working. But now, question is, how to show PRICE AND CUT PRICE at {{ product_item_price }} ???

PLEASE ANSWER.
I am using EMPIRE Shopify Theme by Pixel Union.

[AlKhaleejClinic]

Hi, I successfully changed product list programmatically, shown below.

But when I go to product detail page then it shows the same price which is stored in shopify admin. Although, i changed price there too ash shown below,

but when i click on ADD TO CART, it still shows the price stored on shopify admin as shown below in screenshot, which is not what it should be.

HOW TO APPLY % sale on collection? So when we checkout, there must be new discounted price shown. HOW TO DO THIS??
PLEASE I AM TIRED, HELP ME !!!