Purchasing and contracting procedures, including bidding procedure when it will serve the best interest of the city shall be established by ordinance. The city manager shall be responsible for purchasing and a system of centralized purchasing shall be developed and maintained. The authority to contract in behalf of the city is vested in the council, provided that the city manager shall have the power to bind the city as to routine or operational items. No materials, supplies or public improvements costing more than $1,000 shall be purchased or contracted for except after competitive prices shall have been obtained or requested, except in case of emergency. The council shall have the right to reject any and all bids for work or for the furnishing of materials or supplies to the city. No contract shall be made with any person, firm or corporation in default to the city.