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	$238.71	10.462%	$263.6838	$263.68	$263.70	$263.70
Purchase #2	$40.51	10.377%	$44.7137	$44.71	$44.70	$44.70
Purchase #3	$195.93	10.497%	$216.4968	$216.50	$216.50	$216.50
Purchase #4	$127.39	13.264%	$144.287	$144.29	$144.30	$144.30
Purchase #5	$155.27	7.344%	$166.673	$166.67	$166.65	$166.70
Purchase #6	$56.52	5.399%	$59.5715	$59.57	$59.55	$59.60
Purchase #7	$241.94	6.403%	$257.4314	$257.43	$257.45	$257.40
7 purchase totals =	$1,056.27		$1,152.8572	$1,152.85	$1,152.85	$1,152.90