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	$236.55	12.675%	$266.5327	$266.53	$266.55	$266.50
Purchase #2	$226.51	6.128%	$240.3905	$240.39	$240.40	$240.40
Purchase #3	$174.60	6.422%	$185.8128	$185.81	$185.80	$185.80
Purchase #4	$83.98	8.259%	$90.9159	$90.92	$90.90	$90.90
Purchase #5	$94.83	11.392%	$105.633	$105.63	$105.65	$105.60
Purchase #6	$23.85	13.580%	$27.0888	$27.09	$27.10	$27.10
Purchase #7	$221.29	7.754%	$238.4488	$238.45	$238.45	$238.40
7 purchase totals =	$1,061.61		$1,154.8225	$1,154.82	$1,154.85	$1,154.70