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	$73.27	4.273%	$76.4008	$76.40	$76.40	$76.40
Purchase #2	$49.87	6.809%	$53.2656	$53.27	$53.25	$53.30
Purchase #3	$114.33	8.411%	$123.9463	$123.95	$123.95	$123.90
Purchase #4	$106.47	7.563%	$114.5223	$114.52	$114.50	$114.50
Purchase #5	$204.35	9.646%	$224.0616	$224.06	$224.05	$224.10
Purchase #6	$249.59	10.486%	$275.762	$275.76	$275.75	$275.80
Purchase #7	$240.43	6.262%	$255.4857	$255.49	$255.50	$255.50
7 purchase totals =	$1,038.31		$1,123.4443	$1,123.45	$1,123.40	$1,123.50