Cart

Secondly, a tag like Number of items: 0
Subtotal: €0.00 
*This is a subtotal. Taxes and shipping costs are calculated at time of checkout could be be placed on a page or page template to allow users to see a brief summary of items in the cart. This is typically used in the header of an e-commerce site.

Thirdly, a tag like

Your cart is empty
would be placed on a page or page template to allow users to edit and preview the items in their cart.