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	$201.47	10.590%	$222.8057	$222.81	$222.80	$222.80
Purchase #2	$205.46	8.788%	$223.5158	$223.52	$223.50	$223.50
Purchase #3	$33.61	13.428%	$38.1232	$38.12	$38.10	$38.10
Purchase #4	$139.89	10.681%	$154.8317	$154.83	$154.85	$154.80
Purchase #5	$72.63	5.235%	$76.4322	$76.43	$76.45	$76.40
Purchase #6	$10.68	12.634%	$12.0293	$12.03	$12.05	$12.00
Purchase #7	$50.58	9.840%	$55.5571	$55.56	$55.55	$55.60
7 purchase totals =	$714.32		$783.2950	$783.30	$783.30	$783.20