Thanks to YITH WooCommerce Dynamic Pricing and Discounts, you can create almost any sort of price rule and discounts for your shop, both quantity based discounts and cart discounts.
By combining this plugin with YITH WooCommerce Added to Cart Popup, the discounted price will also be visible in the add-to-cart popup.
To enable this feature, just make sure that the premium version of both plugins has been installed and activated from the Plugins page. No other option needs to be enabled.
Based on the rule settings, the discount that normally shows in the cart will also show up in the added-to-cart popup:
For any further details about YITH WooCommerce Dynamic Pricing and Discounts, please, refer to the official plugin documentation here.