In its decree, the court shall ascertain and determine the amount of taxes, special assessments, and other liens, interest, and costs chargeable to each particular item of real property, excluding any lien on real estate for special assessments levied by any sanitary and improvement district which special assessments have not been previously offered for sale by the county treasurer, and award to the plaintiff an attorney‘s fee, unless waived by the plaintiff, in an amount equal to ten percent of the amount due which shall be taxed as part of the costs in the action and apportioned equitably as other costs.