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	$104.69	11.683%	$116.9209	$116.92	$116.90	$116.90
Purchase #2	$231.41	8.314%	$250.6494	$250.65	$250.65	$250.60
Purchase #3	$46.51	12.716%	$52.4242	$52.42	$52.40	$52.40
Purchase #4	$133.78	11.277%	$148.8664	$148.87	$148.85	$148.90
Purchase #5	$174.81	11.103%	$194.2192	$194.22	$194.20	$194.20
Purchase #6	$135.47	8.406%	$146.8576	$146.86	$146.85	$146.90
Purchase #7	$125.75	9.515%	$137.7151	$137.72	$137.70	$137.70
7 purchase totals =	$952.42		$1,047.6528	$1,047.66	$1,047.55	$1,047.60