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	$214.65	7.140%	$229.976	$229.98	$230.00	$230.00
Purchase #2	$35.89	11.700%	$40.0891	$40.09	$40.10	$40.10
Purchase #3	$191.74	4.720%	$200.7901	$200.79	$200.80	$200.80
Purchase #4	$47.53	6.189%	$50.4716	$50.47	$50.45	$50.50
Purchase #5	$228.57	8.449%	$247.8819	$247.88	$247.90	$247.90
Purchase #6	$52.77	12.850%	$59.5509	$59.55	$59.55	$59.60
Purchase #7	$218.88	9.608%	$239.91	$239.91	$239.90	$239.90
7 purchase totals =	$990.03		$1,068.6696	$1,068.67	$1,068.70	$1,068.80