All city taxes and earnings on such taxes, as provided for in RCW 36.29.020, collected during the month shall be remitted to the city by the county treasurer on or before the tenth day of the following month. The county treasurer shall submit a statement of taxes collected with such remittance. To facilitate the investment of collected taxes, the treasurer may invest as provided for in RCW 36.29.020 without the necessity of the cities specifically requesting combining funds for the purposes of investment.