round price to tick size

I have an issue about rounding price to tick size. Suppose there is price tick table below. what is tick size for price 1001, 1002 ... 1004? In other words, how to handle the price in between upper range of first level and the lower range of next level?

range tick
0 - 50 1
51 - 1000 5
1005 - 1000000 10


EDIT: The tick table is created by myself which is based on the exchange spec.

50 or less: 1
Over 50 up to 1,000: 5
Over 1,000: 10

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Hmm, I've never seen a product have an empty range like that. Can you say which product this is? –  chrisaycock Dec 18 '12 at 3:28
it is index option –  Michael D Dec 18 '12 at 3:47