Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$48.96	7.591%	$52.6766	$52.68	$52.70	$52.70
Purchase #2	$91.81	13.822%	$104.5	$104.50	$104.50	$104.50
Purchase #3	$198.73	3.186%	$205.0615	$205.06	$205.05	$205.10
Purchase #4	$73.83	7.209%	$79.1524	$79.15	$79.15	$79.20
Purchase #5	$191.88	7.285%	$205.8585	$205.86	$205.85	$205.90
Purchase #6	$201.72	10.496%	$222.8925	$222.89	$222.90	$222.90
Purchase #7	$131.52	5.582%	$138.8614	$138.86	$138.85	$138.90
7 purchase totals =	$938.45		$1,009.0029	$1,009.00	$1,009.00	$1,009.20