This is a mini plugin that sets the subtotal in your WooCommerce cart always to the value of the total amount. PHP can have trouble with rounding your price amounts, especially when your shop uses lower, odd price values like 1,99 or 2,73. Add tax calculations to this and you might encounter rounding issues in cart and checkout of your WooCommerce shop.
This mini plugin masks this behaviour.
Somebody pointed out to me that this WooCommerce rounding snippet goes well with my plugin.