I confirm what
@DoumB21 said. There is no guaranteed 'floor' price like 4, 3, 2 letter domains.
However... I can drop you a tip... if your 5 letter .coms contain a full word + a prefix or suffix it has value. Depending on the 'word' and what 'industry' your word relates to, will determine the value. Example i tried to get Fluza.com (Flu + za suffix) yesterday but was out bid. Great name for a flu medicine brand.
Because 5 letters limit what words you can use because of the length, this is why they have value.. they are rare. You can only use 2, 3, and 4 letter words + a short suffix.. which is very limiting.
If you are talking about 5 letter words that just happen to be pronounceable like Zaxxy... then the value is not as guaranteed value as if it contained a known word.
Hope that helps, Cheers!