Does "shouldn't" always take "should" as a question tag?

In simple usage, the question tag always mirrors the clause which makes the statement:

You shouldn't take sugar, should you?
You won't take sugar, will you?

Changing the question tag makes it into a statement and a supplementary question. Note the change in written punctuation, which may not be so obvious in speech.

You shouldn't take sugar; will you? (That is, will you do that anyway?)
You won't take sugar; should you? (That is, should you do that even if you have decided not to?)

The first, normal, usage is a simple question tag to confirm the assumption implied in the statement. The second usage is actually inviting a contradiction of the assumption.