It shall be the duty of every person, firm, or corporation engaging, or continuing in Cullman County in any business taxed hereunder to keep and preserve suitable records of the gross proceeds of such business and such other books or accounts as may be necessary to determine the amount of tax for which he or she or it is liable under this part. Such records shall be kept and preserved for a period of two years and shall be open for examination at any time by the department, or its duly authorized agent.