I have uploaded a free plugin on nopCommerce marketplace, which will help you to display product rating scorecard on product details page. After installing, customer can see all ratings grouped by given stars as below picture.



Currently it's available in latest 3 versions (4.00, 4.10, 4.20) of nopCommerce. You can download it from below link.
https://www.nopcommerce.com/p/5828/ratings-reviews-scorecard.aspx

Please don't forget to give your feedback.