OK. You can't if you use the Test Drive Rules.
You can use a benny to reroll any trait test. You can even keep
spending them until you get the result you want or you run out of
bennies! Take the best of your rolls—spending a benny should
never hurt you, only help. If your original roll is a 5, for example,
and a benny gets you a 4, you keep the original 5 instead.
Bennies cannot normally be spent on damage rolls, rolls on
tables, or anything besides trait rolls. (Soak rolls and certain
Edges do allow other uses of bennies besides rerolling trait
rolls, but these are the exception.) Bennies are not saved up
between sessions, so use ‘em or lose ‘em!