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	$192.96	12.766%	$217.5933	$217.59	$217.60	$217.60
Purchase #2	$6.28	13.444%	$7.1243	$7.12	$7.10	$7.10
Purchase #3	$69.82	11.137%	$77.5959	$77.60	$77.60	$77.60
Purchase #4	$131.99	12.755%	$148.8253	$148.83	$148.85	$148.80
Purchase #5	$165.99	5.521%	$175.1543	$175.15	$175.15	$175.20
Purchase #6	$168.55	10.196%	$185.7354	$185.74	$185.75	$185.70
Purchase #7	$102.42	8.634%	$111.2629	$111.26	$111.25	$111.30
7 purchase totals =	$838.01		$923.2914	$923.29	$923.30	$923.30