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	$76.48	11.206%	$85.0503	$85.05	$85.05	$85.10
Purchase #2	$7.90	12.623%	$8.8972	$8.90	$8.90	$8.90
Purchase #3	$51.42	5.195%	$54.0913	$54.09	$54.10	$54.10
Purchase #4	$22.98	3.683%	$23.8264	$23.83	$23.85	$23.80
Purchase #5	$122.79	4.131%	$127.8625	$127.86	$127.85	$127.90
Purchase #6	$126.98	12.714%	$143.1242	$143.12	$143.10	$143.10
Purchase #7	$120.38	13.793%	$136.984	$136.98	$137.00	$137.00
7 purchase totals =	$528.93		$579.8359	$579.83	$579.85	$579.90