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	$241.56	9.681%	$264.9454	$264.95	$264.95	$264.90
Purchase #2	$115.86	11.685%	$129.3982	$129.40	$129.40	$129.40
Purchase #3	$137.87	5.549%	$145.5204	$145.52	$145.50	$145.50
Purchase #4	$111.76	3.663%	$115.8538	$115.85	$115.85	$115.90
Purchase #5	$71.37	8.485%	$77.4257	$77.43	$77.45	$77.40
Purchase #6	$241.26	6.719%	$257.4703	$257.47	$257.45	$257.50
Purchase #7	$23.78	7.157%	$25.4819	$25.48	$25.50	$25.50
7 purchase totals =	$943.46		$1,016.0957	$1,016.10	$1,016.10	$1,016.10