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	$144.72	9.654%	$158.6913	$158.69	$158.70	$158.70
Purchase #2	$47.89	3.864%	$49.7405	$49.74	$49.75	$49.70
Purchase #3	$205.28	3.785%	$213.0498	$213.05	$213.05	$213.00
Purchase #4	$221.55	13.606%	$251.6941	$251.69	$251.70	$251.70
Purchase #5	$40.92	11.168%	$45.4899	$45.49	$45.50	$45.50
Purchase #6	$11.38	12.336%	$12.7838	$12.78	$12.80	$12.80
Purchase #7	$92.73	8.356%	$100.4785	$100.48	$100.50	$100.50
7 purchase totals =	$764.47		$831.9279	$831.92	$832.00	$831.90