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	$208.95	7.488%	$224.5962	$224.60	$224.60	$224.60
Purchase #2	$217.95	8.103%	$235.6105	$235.61	$235.60	$235.60
Purchase #3	$173.73	6.646%	$185.2761	$185.28	$185.30	$185.30
Purchase #4	$149.31	10.575%	$165.0995	$165.10	$165.10	$165.10
Purchase #5	$109.81	6.112%	$116.5216	$116.52	$116.50	$116.50
Purchase #6	$118.72	6.246%	$126.1353	$126.14	$126.15	$126.10
Purchase #7	$37.92	6.258%	$40.293	$40.29	$40.30	$40.30
7 purchase totals =	$1,016.39		$1,093.5322	$1,093.54	$1,093.55	$1,093.50