Cities and towns having a population of five thousand or less may be chartered alone by general law. They may levy, assess and collect such taxes as may be authorized by law, but no tax for any purpose shall ever be lawful for any one year which shall exceed one and one-half per cent of the taxable property of such city; and all taxes shall be collectible only in current money, and all licenses and occupation taxes levied, and all fines, forfeitures and penalties accruing to said cities and towns shall be collectible only in current money.