Tabs are a word processing thing, and aren't supported by HTML markup - for example I can add them at a code level, and they are completely ignored. Technically that sort of formatting is what "tables" are for, but tables aren't a good idea for use with forum posts.

Easiest thing to do is hard-format the spaces with a non-proportional font. You could switch to the ADVANCED editor, select the COMPUTER CODE style, and then spaces will be maintained.

For example:

One    Two    Three  Four
------ ------ ------ ------
Yes    X      50     No
No     -      3      Yes