How to schedule an action to reliably be performed once every 5 minutes?
Using Rules and Rules scheduler (submodule of Rules) seems to me "a" valid approach.

What you actually need to do is a minor variation of what is explained in the tutorial Hourly tasks using rules scheduler: in your case you should use an offset of 5 minutes (instead of only after 1 hour). And you need to run cron every 5 minutes also (not hourly as in that tutorial).

And as explained also in that tutorial: Initially execute the component manually (from then on every other 5 minutes the rule will be executed again).

Note: How to schedule a regular job using Rules in Drupal 7 is another tutorial that covers this topic.