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	$95.26	4.536%	$99.581	$99.58	$99.60	$99.60
Purchase #2	$224.73	10.674%	$248.7177	$248.72	$248.70	$248.70
Purchase #3	$198.98	3.192%	$205.3314	$205.33	$205.35	$205.30
Purchase #4	$233.93	8.192%	$253.0935	$253.09	$253.10	$253.10
Purchase #5	$216.81	5.401%	$228.5199	$228.52	$228.50	$228.50
Purchase #6	$178.94	3.478%	$185.1635	$185.16	$185.15	$185.20
Purchase #7	$193.83	7.726%	$208.8053	$208.81	$208.80	$208.80
7 purchase totals =	$1,342.48		$1,429.2123	$1,429.21	$1,429.20	$1,429.20