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	$235.82	11.375%	$262.6445	$262.64	$262.65	$262.60
Purchase #2	$11.64	5.581%	$12.2896	$12.29	$12.30	$12.30
Purchase #3	$126.28	4.173%	$131.5497	$131.55	$131.55	$131.50
Purchase #4	$153.94	7.487%	$165.4655	$165.47	$165.45	$165.50
Purchase #5	$128.49	9.266%	$140.3959	$140.40	$140.40	$140.40
Purchase #6	$156.59	10.235%	$172.617	$172.62	$172.60	$172.60
Purchase #7	$103.54	7.167%	$110.9607	$110.96	$110.95	$111.00
7 purchase totals =	$916.30		$995.9229	$995.93	$995.90	$995.90