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	$233.90	13.786%	$266.1455	$266.15	$266.15	$266.10
Purchase #2	$203.67	9.146%	$222.2977	$222.30	$222.30	$222.30
Purchase #3	$102.25	3.191%	$105.5128	$105.51	$105.50	$105.50
Purchase #4	$223.88	6.503%	$238.4389	$238.44	$238.45	$238.40
Purchase #5	$197.84	13.822%	$225.1854	$225.19	$225.20	$225.20
Purchase #6	$250.70	6.435%	$266.8325	$266.83	$266.85	$266.80
Purchase #7	$143.53	5.660%	$151.6538	$151.65	$151.65	$151.70
7 purchase totals =	$1,355.77		$1,476.0666	$1,476.07	$1,476.10	$1,476.00