This confused me as well. Stellars are stored in fixed point, as millionths of a stellar. But there's a tiny anti-spam fee for each payment transaction, so if you've sent money somewhere you may find an extra 0.000010 gone.

A better way to phrase what you just did:

    Maybe the values are stored as a float? But that would be silly, so there must be a better reason.

From FAQs: To prevent spam, each transaction burns 10 microstellars (that is, 0.00001 stellars).

Where do the 10 microstellars go? Are they actually destroyed?

If it's the same as Ripple which this is based on, then the 10 microstellars are destroyed, yes.