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	$172.63	13.766%	$196.3942	$196.39	$196.40	$196.40
Purchase #2	$30.47	8.860%	$33.1696	$33.17	$33.15	$33.20
Purchase #3	$50.67	3.427%	$52.4065	$52.41	$52.40	$52.40
Purchase #4	$46.83	3.397%	$48.4208	$48.42	$48.40	$48.40
Purchase #5	$90.85	5.121%	$95.5024	$95.50	$95.50	$95.50
Purchase #6	$221.80	7.508%	$238.4527	$238.45	$238.45	$238.50
Purchase #7	$19.75	7.439%	$21.2192	$21.22	$21.20	$21.20
7 purchase totals =	$633.00		$685.5654	$685.56	$685.50	$685.60