With Easy Digital Downloads, a cart icon, item quantity, and cart total is shown in Themedd’s secondary menu. As well as being able to completely configure how this is shown from the customizer, it can be easily moved to the primary navigation.

/**
 * Move the EDD cart to the primary menu
 *
 * @return string Position of EDD cart
 */
function themedd_snippet_edd_cart_position() {
	return 'primary_menu';
}
add_filter( 'themedd_edd_cart_position', 'themedd_snippet_edd_cart_position' );

PHP should be added to your child theme's functions.php file.