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	$89.43	7.735%	$96.3474	$96.35	$96.35	$96.30
Purchase #2	$101.71	11.172%	$113.073	$113.07	$113.05	$113.10
Purchase #3	$148.78	13.247%	$168.4889	$168.49	$168.50	$168.50
Purchase #4	$17.77	11.680%	$19.8455	$19.85	$19.85	$19.80
Purchase #5	$63.56	4.724%	$66.5626	$66.56	$66.55	$66.60
Purchase #6	$36.71	10.792%	$40.6717	$40.67	$40.65	$40.70
Purchase #7	$99.58	13.507%	$113.0303	$113.03	$113.05	$113.00
7 purchase totals =	$557.54		$618.0194	$618.02	$618.00	$618.00