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	$138.70	3.527%	$143.5919	$143.59	$143.60	$143.60
Purchase #2	$133.76	4.478%	$139.7498	$139.75	$139.75	$139.70
Purchase #3	$137.87	6.365%	$146.6454	$146.65	$146.65	$146.60
Purchase #4	$148.63	4.229%	$154.9156	$154.92	$154.90	$154.90
Purchase #5	$139.51	8.518%	$151.3935	$151.39	$151.40	$151.40
Purchase #6	$245.55	10.127%	$270.4168	$270.42	$270.40	$270.40
Purchase #7	$10.53	6.209%	$11.1838	$11.18	$11.20	$11.20
7 purchase totals =	$954.55		$1,017.8968	$1,017.90	$1,017.90	$1,017.80