Upon every person, firm or corporation engaged or continuing within this state in the business of contracting to construct, reconstruct or build any public highway, road, bridge, or street, an amount equal to five percent of the gross receipts derived from performance of such contracts. The term "gross receipts" is herein defined to include only those amounts derived and received by the contractor from the performance of such contracts.
Ala. Code § 40-23-50 (1975)