This is actually one of Google’s best practices for mobile retail. Logically though, it depends on the type of products you sell in your store. If generally your visitors only buy a single product, you should send them to the cart right away. If they’re likely to buy more than one product, let them continue shopping (don’t disrupt their experience by sending them to the cart), while giving them the option of checking out or viewing the cart.
#81) When clicking “Add to Cart”, open a modal panel instead of redirecting to the Cart page