In the case of mixed uses, the parking spaces required shall equal the sum of the requirements of the various uses computed separately. Up to sixty percent (60%) of the parking spaces required for a theater or other place of evening entertainment, or for a church, may be provided and used jointly by banks, offices, and similar uses not normally open, used, or operated during evening hours if specifically approved by the Planning and Zoning Commission. Such approval may be rescinded by the City Council and additional parking shall be obtained by the owners in the event that the City Council determines that such joint use is resulting in a public nuisance by providing an inadequate number of parking spaces or otherwise adversely affecting the public health, safety, or welfare.