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	$161.34	8.103%	$174.4134	$174.41	$174.40	$174.40
Purchase #2	$110.48	12.658%	$124.4646	$124.46	$124.45	$124.50
Purchase #3	$228.70	9.695%	$250.8725	$250.87	$250.85	$250.90
Purchase #4	$111.77	13.471%	$126.8265	$126.83	$126.85	$126.80
Purchase #5	$31.80	4.409%	$33.2021	$33.20	$33.20	$33.20
Purchase #6	$98.55	13.367%	$111.7232	$111.72	$111.70	$111.70
Purchase #7	$146.82	3.255%	$151.599	$151.60	$151.60	$151.60
7 purchase totals =	$889.46		$973.1013	$973.09	$973.05	$973.10