Don’t redirect to the cart
This is actually one of Google’s best practices for mobile retail. If generally your visitors only buy a single product, I understand the temptation to redirect them directly to the cart. However, that breaks their expectation of an Add to Cart button. One solution is to switch the call to action button to a “Buy” button. Otherwise, I recommend keep it to a regular Add to Cart button which simply adds the product to cart. Let them open their cart if they want to checkout.
A member tested it out
Granted, it is not statistically significant, but still something to consider.
I tested redirecting to the cart page after adding to cart, and I saw a tremendous drop in conversions. I only left it for 2 days, but that was enough for me after 0 purchases.