Every person engaging or continuing in the city any business or exercising any privilege subject to a license tax shall keep and preserve suitable records of the average annual inventory of stock on hand, records sufficient to show the number of employees and a record of all goods and merchandise purchased or received for resale. Every such person shall keep and preserve, for a period of two years, all invoices of goods and merchandise purchased or received for resale and the employment records of all employees and shall furnish such records to the city treasurer for inspection upon request.