In prestashop 1.7, the order total is not shown in the shopping cart. To do so, we must edit the file:
themes/classic/templates/checkout/_partials/cart-summary-totals.tpl
and add this code where you want to show the total of the cart:
<span class="value">{$currency.iso_code}{$currency.sign}{$cart.totals.total.amount+$cart.subtotals.tax.amount}</span>