When any person is committed to any jail by any process issued under authority of the United States, the sheriff or jailer shall receive such person into custody, and safely keep the person until discharged by due course of law, subject in all respects to the same liabilities and remedies as though committed under process issued under state authority. The United States shall pay to the county the minimum sum of $5 per day for each prisoner so kept and boarded. Provided, that in any county of this state, the sheriff shall at the request of the county board of commissioners determine the average daily per capita cost for the food, clothing, medical and incidental expense for the care and maintenance of persons committed to the county jail for the preceding year. The amount found to be the average daily per capita cost of such committed persons shall be paid to the county by the United States for each prisoner so kept and boarded during the current year.