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	$212.96	4.662%	$222.8882	$222.89	$222.90	$222.90
Purchase #2	$25.42	8.601%	$27.6064	$27.61	$27.60	$27.60
Purchase #3	$230.51	11.184%	$256.2902	$256.29	$256.30	$256.30
Purchase #4	$46.28	13.868%	$52.6981	$52.70	$52.70	$52.70
Purchase #5	$59.57	13.274%	$67.4773	$67.48	$67.50	$67.50
Purchase #6	$229.91	6.852%	$245.6634	$245.66	$245.65	$245.70
Purchase #7	$241.80	3.670%	$250.6741	$250.67	$250.65	$250.70
7 purchase totals =	$1,046.45		$1,123.2977	$1,123.30	$1,123.30	$1,123.40