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	$99.34	6.371%	$105.669	$105.67	$105.65	$105.70
Purchase #2	$203.56	11.680%	$227.3358	$227.34	$227.35	$227.30
Purchase #3	$205.71	5.671%	$217.3758	$217.38	$217.40	$217.40
Purchase #4	$106.96	4.356%	$111.6192	$111.62	$111.60	$111.60
Purchase #5	$7.95	3.403%	$8.2205	$8.22	$8.20	$8.20
Purchase #6	$237.42	11.823%	$265.4902	$265.49	$265.50	$265.50
Purchase #7	$170.94	13.762%	$194.4648	$194.46	$194.45	$194.50
7 purchase totals =	$1,031.88		$1,130.1753	$1,130.18	$1,130.15	$1,130.20