Use this shortcode to yourtheme/functions.php or any snippet plugin to do it

if(!function_exists('custom_pos_disable_cash'))
{
    function custom_pos_disable_cash($session_response_data){

        $session_response_data['setting']['pos_disable_cash'] = 'yes';
        $session_response_data['setting']['pos_default_payment'] = 'op_authorize_net_magnetic'; // change to your payment code 
        

        return $session_response_data;
    }
}
add_filter('op_get_login_cashdrawer_data','custom_pos_disable_cash',20,1);