How to roll a 7+ on 1d6

TONKS, by apocrypha_now, is an adorable little minis game which uses minis-standard D6 rolls, where you need to roll a 4+ or 5+ or 6+ a lot of the time to hit various things. This is a very common system for wargames, where you often want to roll several troops at once. The numbers are low, the math is easy, the die is common.

However...

With this kind of system, what do you do when the target number goes above 6, or below 2?

A sensible solution on D6 is to assume that if you need a 7+ or worse, you can never hit, where as a 1+ or better always hits.

(Note that this is not a common D20 rule, which is to say that a 20 always hits and a 1 always misses, no matter what the actual TN.)

In TONKS target numbers can get up into 7+ or higher ranges pretty easily and it doesn't make sense to say these auto-miss. In fact from watching a tiny AP of it probably all the TNs could come down by one. (Heck, because TONKS is a single unit kind of game it could probably have a 2D6 hit roll like CAR WARS; single D6 rolls make the most sense for masses of minis. OTOH there is a lot to be said for a flat distribution without too many buckets. But that's a different topic.)

TONKS resolves this in a very cute / clever way! If you need higher than a 6+, you roll 2D6, and succeed if you roll EXACTLY the target number. This scales nicely from 6/36 down to 1/36 at 12+.  There's the silght issue that a 6+ is just as easy to hit as a 7+, but I'm okay with that.

But is it possible to do better? With something that would work for minis figures where you need to do multiple at once?

Another Cute Idea...

So what about a true open-ended solution?  I'm sure this has been thought of before, even by myself, but I think it's worth writing down.

If you roll a 6, add 5 to the sum and reroll, and repeat on 6's only. (Smooth explosion.)

If you roll a 1, subtract 5 from the sum and reroll, and repeat on 1's only. (Smooth implosion!)

It's pretty easy to add and subtract 5 so you can do it on the side. For example if the target number you need is a 9, that's 5+4, therefore: you need to roll a six then a four.

So there you have it, a D6 system that can handle an infinite range of target numbers, in a symmetrical, strictly monotonic way.