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	$163.28	10.157%	$179.8643	$179.86	$179.85	$179.90
Purchase #2	$13.85	4.341%	$14.4512	$14.45	$14.45	$14.50
Purchase #3	$17.83	12.679%	$20.0907	$20.09	$20.10	$20.10
Purchase #4	$126.50	12.513%	$142.3289	$142.33	$142.35	$142.30
Purchase #5	$49.53	4.420%	$51.7192	$51.72	$51.70	$51.70
Purchase #6	$76.46	8.240%	$82.7603	$82.76	$82.75	$82.80
Purchase #7	$140.68	13.773%	$160.0559	$160.06	$160.05	$160.10
7 purchase totals =	$588.13		$651.2705	$651.27	$651.25	$651.40