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	$168.34	9.733%	$184.7245	$184.72	$184.70	$184.70
Purchase #2	$43.28	6.756%	$46.204	$46.20	$46.20	$46.20
Purchase #3	$45.89	6.159%	$48.7164	$48.72	$48.70	$48.70
Purchase #4	$84.33	13.326%	$95.5678	$95.57	$95.55	$95.60
Purchase #5	$35.75	9.505%	$39.148	$39.15	$39.15	$39.10
Purchase #6	$28.88	8.475%	$31.3276	$31.33	$31.35	$31.30
Purchase #7	$117.69	4.549%	$123.0437	$123.04	$123.05	$123.00
7 purchase totals =	$524.16		$568.7320	$568.73	$568.70	$568.60