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	$141.87	13.798%	$161.4452	$161.45	$161.45	$161.40
Purchase #2	$99.68	11.481%	$111.1243	$111.12	$111.10	$111.10
Purchase #3	$159.71	3.570%	$165.4116	$165.41	$165.40	$165.40
Purchase #4	$249.47	10.499%	$275.6619	$275.66	$275.65	$275.70
Purchase #5	$178.59	13.669%	$203.0015	$203.00	$203.00	$203.00
Purchase #6	$145.60	4.350%	$151.9336	$151.93	$151.95	$151.90
Purchase #7	$151.62	8.730%	$164.8564	$164.86	$164.85	$164.90
7 purchase totals =	$1,126.54		$1,233.4345	$1,233.43	$1,233.40	$1,233.40