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	$53.47	11.288%	$59.5057	$59.51	$59.50	$59.50
Purchase #2	$10.70	8.414%	$11.6003	$11.60	$11.60	$11.60
Purchase #3	$177.27	12.406%	$199.2621	$199.26	$199.25	$199.30
Purchase #4	$151.69	9.715%	$166.4267	$166.43	$166.45	$166.40
Purchase #5	$137.53	13.145%	$155.6083	$155.61	$155.60	$155.60
Purchase #6	$214.36	11.181%	$238.3276	$238.33	$238.35	$238.30
Purchase #7	$184.38	9.801%	$202.4511	$202.45	$202.45	$202.50
7 purchase totals =	$929.40		$1,033.1818	$1,033.19	$1,033.20	$1,033.20