What is TieBreak Tens?
The whole match is one ten-point tiebreak. No games, no sets, no deuce. First to ten points takes the match, and you still have to win by two, so it can run on to 12-10.
How it is played
Rock, paper, scissors decides who serves first. The loser chooses the end. From there it is one tiebreak game, start to finish, with points counted one, two, three rather than 15 and 30.
The first server takes a single point, the other side takes the next two, and it alternates in twos from there. Ends change every six points, on the total of both scores.
Ten points wins it with a margin of two. 10-8 is a result; 9-9 keeps going, and the event's own rules give 11-9 and 13-15 as the kind of scores that follow.
Where it came from
The format is not in the main rules of tennis. The ten-point tiebreak is: the rule book carries it as a way of replacing a deciding set. TieBreak Tens takes that same game and puts nothing in front of it, so whatever standing it has as a competition, the scoring inside it is the tiebreak the rule book already describes, and a whole match fits inside one court booking.
It is not a match tiebreak
A match tiebreak arrives at one set all, and decides a match that has already had two sets played in it. TieBreak Tens is the entire match. The scoring inside the game is identical, which is exactly why the two get confused.
When a club reaches for it
Round robins, box leagues, club nights and anything where courts run back to back and every match has to finish on the hour. It is also a fair way to settle a match that ran out of daylight, as long as both sides agree to it before the first serve rather than after.
In the rule book
Appendix VI of the ITF Rules of Tennis carries the ten-point tiebreak twice: as a match tiebreak in place of a deciding set (VI.4) and as a final-set tiebreak at six games all (VI.5). The two are worded slightly differently but score identically. VI.4 puts it this way:
The first player/team to win ten points shall win the match tie-break and the match provided there is a margin of two points over the opponent(s). If necessary, the match tie-break game shall continue until this margin is achieved.
TieBreak Tens is that game on its own, with nothing before it.
Common follow-ups
Who serves first in TieBreak Tens?
Rock, paper, scissors, which is the official answer and not a joke. The winner serves first and the loser chooses the end, so the two decisions are split between you the way a toss splits them under Rule 9. Playing it yourselves you can just toss for it, as long as one side does not get both.
Do you change ends?
Yes, every six points, counted on the total of both scores rather than either one. Play it under the ordinary rules of tennis and you swap without sitting down, because Rule 29a makes play continuous through a tiebreak and this format is all tiebreak.
Is there a let on serve?
Yes, unless the event has said otherwise. The no-let rule is a separate alternative in Appendix VI and has nothing to do with playing a tiebreak.
Luasc has TieBreak Tens as a format of its own, so the watch counts a tiebreak from the first point instead of pretending there is a set underneath it. The rest of the formats.