It shall be the duty of every person subject to this article to keep and preserve suitable records of all sales made by him or her, and such other books or accounts as may be necessary to determine the amount of sales tax and use tax, the collection or payment for which he or she is liable under this article. If such person cannot produce records suitable, in the judgment of the tax administrator, to support his or her actual sales/use tax liability, the tax administrator may establish the liability by use of generally acceptable accounting principles, including making estimates. Furthermore, when suitable records are available but, in the judgment of the tax administrator, are so voluminous that excessive and undue time would be required to conduct an actual audit thereof, the tax administrator may use a test-period audit or other appropriate sampling techniques to compute the sales/use tax liability. It shall be the duty of every such person to keep and preserve for a period of three years all invoices of goods and merchandise purchased for resale or use in the business, and all such books, invoices and other records shall be open for examination at any time and by the finance director or his or her duly authorized agents at a location within the City. The taxpayer may elect to pay the expenses involved in conducting the audit at a location outside the City if it is not possible for him or her to provide the necessary records within the City. The finance director, in his or her discretion, may elect to conduct the audit at the taxpayer's principal place of business. If this occurs, the city shall pay the expenses involved in conducting the audit if such place of business is located outside the City. (Code 1979, § 36-25)