We need more granularity on fee amount. Also it was rounding down

    $ clamd help settxfee
    settxfee <amount>
    <amount> is a real and is rounded to the nearest 0.01

Two problems: 0.01 is too big - the default is 0.0001.
And it wasn't rounding to the nearest, it was rounding down.

This fixes both of those problems.