Taxes is not shown in the cart. Using Drupal Commerce module
Drupal commerce will by default not show taxes on the cart, the cart is more simple minded with focus on products. The review and checkout pages, will however have taxes displayed by default.

The shopping cart is based on views, so it's pretty easy to change how the order total is displayed. Instead of using Commerce Line Item: Line item summary area handler you should instead use the Commerce Order: Total