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	$236.87	9.176%	$258.6052	$258.61	$258.60	$258.60
Purchase #2	$232.82	9.731%	$255.4757	$255.48	$255.50	$255.50
Purchase #3	$230.61	13.695%	$262.192	$262.19	$262.20	$262.20
Purchase #4	$99.98	8.534%	$108.5123	$108.51	$108.50	$108.50
Purchase #5	$106.32	10.858%	$117.8642	$117.86	$117.85	$117.90
Purchase #6	$105.45	5.846%	$111.6146	$111.61	$111.60	$111.60
Purchase #7	$31.57	9.271%	$34.4969	$34.50	$34.50	$34.50
7 purchase totals =	$1,043.62		$1,148.7609	$1,148.76	$1,148.75	$1,148.80