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	$100.94	10.827%	$111.8688	$111.87	$111.85	$111.90
Purchase #2	$203.74	4.224%	$212.346	$212.35	$212.35	$212.30
Purchase #3	$11.72	13.461%	$13.2976	$13.30	$13.30	$13.30
Purchase #4	$115.71	13.532%	$131.3679	$131.37	$131.35	$131.40
Purchase #5	$43.37	11.350%	$48.2925	$48.29	$48.30	$48.30
Purchase #6	$59.76	11.198%	$66.4519	$66.45	$66.45	$66.50
Purchase #7	$166.63	4.114%	$173.4852	$173.49	$173.50	$173.50
7 purchase totals =	$701.87		$757.1099	$757.12	$757.10	$757.20