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	$89.88	5.733%	$95.0328	$95.03	$95.05	$95.00
Purchase #2	$51.86	3.282%	$53.562	$53.56	$53.55	$53.60
Purchase #3	$128.47	9.293%	$140.4087	$140.41	$140.40	$140.40
Purchase #4	$166.60	4.365%	$173.8721	$173.87	$173.85	$173.90
Purchase #5	$45.57	9.475%	$49.8878	$49.89	$49.90	$49.90
Purchase #6	$42.39	13.397%	$48.069	$48.07	$48.05	$48.10
Purchase #7	$61.83	3.307%	$63.8747	$63.87	$63.85	$63.90
7 purchase totals =	$586.60		$624.7071	$624.70	$624.65	$624.80