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	$103.83	11.806%	$116.0882	$116.09	$116.10	$116.10
Purchase #2	$210.56	6.204%	$223.6231	$223.62	$223.60	$223.60
Purchase #3	$108.46	3.656%	$112.4253	$112.43	$112.45	$112.40
Purchase #4	$82.59	9.397%	$90.351	$90.35	$90.35	$90.40
Purchase #5	$42.67	9.159%	$46.5781	$46.58	$46.60	$46.60
Purchase #6	$165.90	4.788%	$173.8433	$173.84	$173.85	$173.80
Purchase #7	$11.58	9.340%	$12.6616	$12.66	$12.65	$12.70
7 purchase totals =	$725.59		$775.5706	$775.57	$775.60	$775.60