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	$217.52	5.235%	$228.9072	$228.91	$228.90	$228.90
Purchase #2	$143.47	4.652%	$150.1442	$150.14	$150.15	$150.10
Purchase #3	$81.70	7.386%	$87.7344	$87.73	$87.75	$87.70
Purchase #4	$11.54	9.210%	$12.6028	$12.60	$12.60	$12.60
Purchase #5	$47.80	6.409%	$50.8635	$50.86	$50.85	$50.90
Purchase #6	$79.41	5.568%	$83.8315	$83.83	$83.85	$83.80
Purchase #7	$92.85	6.793%	$99.1573	$99.16	$99.15	$99.20
7 purchase totals =	$674.29		$713.2409	$713.23	$713.25	$713.20