I ended up going off of this response, but it only shows the discounted price on the main pages and in collections, not the actual individual item. Since it changes the code, I duplicated the theme and named it "sale" for this purpose. Just remember ...

This helped on the collection and pain pages, but the actual product pages still show the full price. How can I change the product pages as well?

Which liquid file did you edit to get the strike through?