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	$210.72	13.739%	$239.6708	$239.67	$239.65	$239.70
Purchase #2	$158.84	9.291%	$173.5978	$173.60	$173.60	$173.60
Purchase #3	$105.72	6.484%	$112.5749	$112.57	$112.55	$112.60
Purchase #4	$221.55	11.756%	$247.5954	$247.60	$247.60	$247.60
Purchase #5	$90.28	11.214%	$100.404	$100.40	$100.40	$100.40
Purchase #6	$143.48	3.520%	$148.5305	$148.53	$148.55	$148.50
Purchase #7	$154.38	5.341%	$162.6254	$162.63	$162.65	$162.60
7 purchase totals =	$1,084.97		$1,184.9988	$1,185.00	$1,185.00	$1,185.00