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	$152.80	9.451%	$167.2411	$167.24	$167.25	$167.20
Purchase #2	$11.32	10.109%	$12.4643	$12.46	$12.45	$12.50
Purchase #3	$233.46	11.628%	$260.6067	$260.61	$260.60	$260.60
Purchase #4	$42.66	9.291%	$46.6235	$46.62	$46.60	$46.60
Purchase #5	$145.92	13.545%	$165.6849	$165.68	$165.70	$165.70
Purchase #6	$82.64	11.499%	$92.1428	$92.14	$92.15	$92.10
Purchase #7	$63.40	4.409%	$66.1953	$66.20	$66.20	$66.20
7 purchase totals =	$732.20		$810.9586	$810.95	$810.95	$810.90