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	$177.47	10.769%	$196.5817	$196.58	$196.60	$196.60
Purchase #2	$38.27	7.103%	$40.9883	$40.99	$41.00	$41.00
Purchase #3	$102.67	8.805%	$111.7101	$111.71	$111.70	$111.70
Purchase #4	$158.37	7.399%	$170.0878	$170.09	$170.10	$170.10
Purchase #5	$50.84	4.599%	$53.1781	$53.18	$53.20	$53.20
Purchase #6	$239.55	10.831%	$265.4957	$265.50	$265.50	$265.50
Purchase #7	$154.90	9.509%	$169.6294	$169.63	$169.65	$169.60
7 purchase totals =	$922.07		$1,007.6711	$1,007.68	$1,007.75	$1,007.70