Lots or tracts may be sold or transferred as a single group or unit or in more than one group or unit either:

(a) Upon the motion of any party to the action and the court grants such motion by order after making a finding that any two or more lots or tracts constitute a single unit for usual uses and will sell for a higher price if sold together; or

(b) by the county, without a court order, if such lots or tracts previously have been offered at public auction for delinquent property taxes, but which did not sell at the previous public auction.