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	$143.42	5.667%	$151.5476	$151.55	$151.55	$151.50
Purchase #2	$29.59	6.843%	$31.6148	$31.61	$31.60	$31.60
Purchase #3	$249.27	13.462%	$282.8267	$282.83	$282.85	$282.80
Purchase #4	$138.49	8.468%	$150.2173	$150.22	$150.20	$150.20
Purchase #5	$166.75	3.214%	$172.1093	$172.11	$172.10	$172.10
Purchase #6	$10.65	7.137%	$11.4101	$11.41	$11.40	$11.40
Purchase #7	$215.26	4.868%	$225.7389	$225.74	$225.75	$225.70
7 purchase totals =	$953.43		$1,025.4647	$1,025.47	$1,025.45	$1,025.30