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	$148.47	5.709%	$156.9462	$156.95	$156.95	$156.90
Purchase #2	$250.27	6.149%	$265.6591	$265.66	$265.65	$265.70
Purchase #3	$176.72	11.174%	$196.4667	$196.47	$196.45	$196.50
Purchase #4	$200.77	11.553%	$223.965	$223.97	$223.95	$224.00
Purchase #5	$60.80	6.670%	$64.8554	$64.86	$64.85	$64.90
Purchase #6	$46.51	11.509%	$51.8628	$51.86	$51.85	$51.90
Purchase #7	$17.37	13.565%	$19.7262	$19.73	$19.75	$19.70
7 purchase totals =	$900.91		$979.4814	$979.50	$979.45	$979.60