When products are added to the cart there is a Notice pop-up box, which prompts whether to continue shopping or to navigate to the cart.
You can easily disable the checkout Notice pop-up box.
Navigate to your Joomla administrator area->Components->VirtueMart->Admin-> Configuration->Site.
Click on the Configuration link besides the Select the theme for your Shop drop-down menu.
There set the following values:
Customer Checkout in a popup (GreyBox)? No
Use Ajax to add, update or delete products from the cart? No
Save the changes and test the new functionality. Once you order an item you will be redirected to the cart page.