Theoretically, yes. If the required to-hit number is modified to, say, 12 or more, you would do the following:
1) Roll your initial dice.
2) If any come up 6, reroll them and add 5.
3) If any of THOSE come up 6, reroll them and add 10.
Thus, to achieve a 12, you would need to roll a 6, then another 6, and then a 2 or more (2+10=12).
However, the need for such a thing is remote at best. I am hard-pressed to think of any set of circumstances that would apply a -6 modifier or worse.