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	$56.28	8.425%	$61.0216	$61.02	$61.00	$61.00
Purchase #2	$146.83	7.683%	$158.1109	$158.11	$158.10	$158.10
Purchase #3	$44.72	3.274%	$46.1841	$46.18	$46.20	$46.20
Purchase #4	$154.42	11.629%	$172.3775	$172.38	$172.40	$172.40
Purchase #5	$237.91	10.302%	$262.4195	$262.42	$262.40	$262.40
Purchase #6	$140.94	12.473%	$158.5194	$158.52	$158.50	$158.50
Purchase #7	$122.55	6.695%	$130.7547	$130.75	$130.75	$130.80
7 purchase totals =	$903.65		$989.3877	$989.38	$989.35	$989.40