I've searched from cacti.net forum and other blogs to no avail. With all those research done on how to work with cron jobs, I managed to make my cacti system poll every minute through cron. So here is what I have done.
Add this line on your crontab, this will schedule your poller.php to run every minute.
*/1 * * * * php /var/www/cacti/poller.php > /dev/null 2>&1
For any reason that when you typed 'crontab -e' and get an error like 'no crontab for root, just create a 'cron' folder on /var/spool and then repeat the 'crontab -e' procedure above. Upon exit, the crontab details will then saved on /var/spool/cron/root
My cacti is now polling every minute but the polling intervals on my graphs are still at 5 minutes. For now, I haven't found a solution yet on how to make the 1 minute data to reflect on my graphs.