wp_schedule_event に5分間隔のイベントを追加

add_filter('cron_schedules',function($schedules){
    $schedules['five_minutes'] = array(
            'interval'  => 300,
            'display'   => __('Every 5 Minutes')
    );
    return $schedules;
});

wp_schedule_event(time(), 'five_minutes', 'your_cron_function');

参照