Domino's Pizza continued lifting sales and profits in the half year to 26 June in spite of the tough economic environment.The pizza delivery group said sales rose by 15% from the same period the previous year to £196.4m, while pre-tax profits were up by 25% to £13.6m. Domino's lifted the dividend by 30% to 3.5p.Sales were helped by heavy price promotions, with Domino's able to benefit from lower advertising prices to advertise its pizza deals.The firm, which currently operates 576 stores in the UK and Ireland, said it is still on track for 50 new store openings this year.Chief executive Chris Moore said the firm is on track to exceed market expectations for the full year.