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	$206.85	11.852%	$231.3659	$231.37	$231.35	$231.40
Purchase #2	$181.78	4.293%	$189.5838	$189.58	$189.60	$189.60
Purchase #3	$172.54	5.275%	$181.6415	$181.64	$181.65	$181.60
Purchase #4	$10.98	9.382%	$12.0101	$12.01	$12.00	$12.00
Purchase #5	$194.70	13.512%	$221.0079	$221.01	$221.00	$221.00
Purchase #6	$228.38	12.432%	$256.7722	$256.77	$256.75	$256.80
Purchase #7	$156.85	10.162%	$172.7891	$172.79	$172.80	$172.80
7 purchase totals =	$1,152.08		$1,265.1705	$1,265.17	$1,265.15	$1,265.20