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	$70.78	5.203%	$74.4627	$74.46	$74.45	$74.50
Purchase #2	$89.56	10.485%	$98.9504	$98.95	$98.95	$99.00
Purchase #3	$189.37	5.524%	$199.8308	$199.83	$199.85	$199.80
Purchase #4	$145.63	3.400%	$150.5814	$150.58	$150.60	$150.60
Purchase #5	$46.70	13.132%	$52.8326	$52.83	$52.85	$52.80
Purchase #6	$83.51	7.395%	$89.6856	$89.69	$89.70	$89.70
Purchase #7	$32.74	6.465%	$34.8566	$34.86	$34.85	$34.90
7 purchase totals =	$658.29		$701.2001	$701.20	$701.25	$701.30