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	$155.31	4.165%	$161.7787	$161.78	$161.80	$161.80
Purchase #2	$186.89	7.429%	$200.7741	$200.77	$200.75	$200.80
Purchase #3	$84.72	3.528%	$87.7089	$87.71	$87.70	$87.70
Purchase #4	$154.25	12.609%	$173.6994	$173.70	$173.70	$173.70
Purchase #5	$206.81	8.204%	$223.7767	$223.78	$223.80	$223.80
Purchase #6	$195.46	11.217%	$217.3847	$217.38	$217.40	$217.40
Purchase #7	$18.46	10.726%	$20.44	$20.44	$20.45	$20.40
7 purchase totals =	$1,001.90		$1,085.5625	$1,085.56	$1,085.60	$1,085.60