It is more a personality classification than a sanity check. Providing you don't come across as a habitual risk taker, or lacking in determination, it's really a case of trying to judge whether you'd fit in.
They can be useful, if administered properly in conjuction with interviews and not taken too seriously.
Best advice is to try to visualise in advance the kind of person you would employ if you were them and try to answer from that point of view. Don't try to speculate what the right answers are to individual questions or the inconsistencies will show up.
Some firms don't worry much about what kind of personality the test indicates, but simply reject candidates that give inconsistent answers on the basis that they are probably bull!!!!ters.