Hello Tom!
I contacted the support of the coin plugin and this was the response of the developer:
“Hi Pedro,
I checked your site, and It seems a problem relate to the “sticky add to cart” code. The “sticky add to cart” code is using the function product->get_price() instead of $product->get_price_html(). For variable products, the $product->get_price() function returns the value of the database without apply the round function.
This code issue is causing another problem: the “Load product price in the background” function can’t refresh the “sticky add to cart” price, because it does not include the PBoC classes.”