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	$53.57	5.654%	$56.5988	$56.60	$56.60	$56.60
Purchase #2	$20.92	3.341%	$21.6189	$21.62	$21.60	$21.60
Purchase #3	$112.27	4.445%	$117.2604	$117.26	$117.25	$117.30
Purchase #4	$13.53	6.442%	$14.4016	$14.40	$14.40	$14.40
Purchase #5	$34.50	11.483%	$38.4616	$38.46	$38.45	$38.50
Purchase #6	$52.75	5.771%	$55.7942	$55.79	$55.80	$55.80
Purchase #7	$50.86	5.610%	$53.7132	$53.71	$53.70	$53.70
7 purchase totals =	$338.40		$357.8487	$357.84	$357.80	$357.90