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	$167.52	13.471%	$190.0866	$190.09	$190.10	$190.10
Purchase #2	$91.61	4.110%	$95.3752	$95.38	$95.40	$95.40
Purchase #3	$18.87	8.528%	$20.4792	$20.48	$20.50	$20.50
Purchase #4	$11.87	10.621%	$13.1307	$13.13	$13.15	$13.10
Purchase #5	$20.41	10.628%	$22.5792	$22.58	$22.60	$22.60
Purchase #6	$161.39	13.341%	$182.921	$182.92	$182.90	$182.90
Purchase #7	$38.69	10.617%	$42.7977	$42.80	$42.80	$42.80
7 purchase totals =	$510.36		$567.3696	$567.38	$567.45	$567.40