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	$90.87	9.517%	$99.5181	$99.52	$99.50	$99.50
Purchase #2	$148.62	4.269%	$154.9646	$154.96	$154.95	$155.00
Purchase #3	$130.93	9.530%	$143.4076	$143.41	$143.40	$143.40
Purchase #4	$63.31	6.379%	$67.3485	$67.35	$67.35	$67.30
Purchase #5	$242.73	5.446%	$255.9491	$255.95	$255.95	$255.90
Purchase #6	$77.99	5.733%	$82.4612	$82.46	$82.45	$82.50
Purchase #7	$140.89	5.653%	$148.8545	$148.85	$148.85	$148.90
7 purchase totals =	$895.34		$952.5036	$952.50	$952.45	$952.50