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	$62.67	6.710%	$66.8752	$66.88	$66.90	$66.90
Purchase #2	$243.39	13.169%	$275.442	$275.44	$275.45	$275.40
Purchase #3	$129.88	7.625%	$139.7834	$139.78	$139.80	$139.80
Purchase #4	$189.49	4.382%	$197.7935	$197.79	$197.80	$197.80
Purchase #5	$127.72	13.821%	$145.3722	$145.37	$145.35	$145.40
Purchase #6	$160.55	5.602%	$169.544	$169.54	$169.55	$169.50
Purchase #7	$143.83	5.209%	$151.3221	$151.32	$151.30	$151.30
7 purchase totals =	$1,057.53		$1,146.1324	$1,146.12	$1,146.15	$1,146.10