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	$56.59	8.620%	$61.4681	$61.47	$61.45	$61.50
Purchase #2	$177.76	5.219%	$187.0373	$187.04	$187.05	$187.00
Purchase #3	$221.25	11.856%	$247.4814	$247.48	$247.50	$247.50
Purchase #4	$10.90	12.376%	$12.249	$12.25	$12.25	$12.20
Purchase #5	$63.55	6.733%	$67.8288	$67.83	$67.85	$67.80
Purchase #6	$124.78	3.139%	$128.6968	$128.70	$128.70	$128.70
Purchase #7	$48.56	10.517%	$53.6671	$53.67	$53.65	$53.70
7 purchase totals =	$703.39		$758.4285	$758.44	$758.45	$758.40