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	$182.26	13.381%	$206.6482	$206.65	$206.65	$206.60
Purchase #2	$174.51	12.439%	$196.2173	$196.22	$196.20	$196.20
Purchase #3	$151.28	13.381%	$171.5228	$171.52	$171.50	$171.50
Purchase #4	$106.60	7.414%	$114.5033	$114.50	$114.50	$114.50
Purchase #5	$128.41	11.712%	$143.4494	$143.45	$143.45	$143.40
Purchase #6	$52.85	11.317%	$58.831	$58.83	$58.85	$58.80
Purchase #7	$237.31	9.381%	$259.5721	$259.57	$259.55	$259.60
7 purchase totals =	$1,033.22		$1,150.7441	$1,150.74	$1,150.70	$1,150.60