Well, the thing is it's not "my 5 ". A rating is something the buyer can leave and it's up to their discretion. You may feel you earned 5, a buyer may feel, maybe compared to what they got from another seller, that 4* reflect the service. Then, there are those "nothing is perfect, it always could be more, faster, better, cheaper..." buyers.

I'd be extremely cautious with asking, there have been people reporting the buyers changed the rating to even less stars. The buyer may feel harrassed if you ask and even report you, after all Fiverr says they discourage asking for a review change.

Then of course, you may be lucky and the buyer will give you a better review.

Also there was this Bugs where buyers wanted to rate 5 * but the app managed to make it 4.3 or 4.7 I believe, don't know if that bug is still around.

In summary, nobody can decide that for you.

And if you want to do another job for that buyer, be extremely cautious how you word it if you want to mention the 5* issue. Anything that vaguely looks like "harassment", "my account depends on 5*", begging, promising better work, bonus work, etc. is a big no-no. People got account warnings for that. And even if you don't see it as begging, the buyer and CS might. Proceed with caution.

Personally, I'd probably swallow the 4 * and tell the buyer something like sorry, seeing your rating of the job I did for you, I think you'd better find another seller to work with. Depending on how many reviews you have, one 4* every once in a while won't kill you probably, but several, maybe even in a row, might.