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	$21.90	4.404%	$22.8645	$22.86	$22.85	$22.90
Purchase #2	$99.58	12.318%	$111.8463	$111.85	$111.85	$111.80
Purchase #3	$47.85	7.532%	$51.4541	$51.45	$51.45	$51.50
Purchase #4	$170.92	11.370%	$190.3536	$190.35	$190.35	$190.40
Purchase #5	$20.60	7.840%	$22.215	$22.22	$22.20	$22.20
Purchase #6	$66.81	5.331%	$70.3716	$70.37	$70.35	$70.40
Purchase #7	$217.27	3.796%	$225.5176	$225.52	$225.50	$225.50
7 purchase totals =	$644.93		$694.6227	$694.62	$694.55	$694.70