When taking the exit it's moot. By the time you've put it on you're already half way off.
On approach, you can signal left for the benefit of those at waiting at your exit point if there is only a single lane (if there's multiple, it's, once again, rather moot. Most of the traffic will be locals and people who frequent those roads and road position will tell them) entering the mini roundabout, but only if straight ahead is the first exit.