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	$12.83	12.724%	$14.4625	$14.46	$14.45	$14.50
Purchase #2	$78.76	4.556%	$82.3483	$82.35	$82.35	$82.30
Purchase #3	$110.67	12.733%	$124.7616	$124.76	$124.75	$124.80
Purchase #4	$45.78	6.243%	$48.638	$48.64	$48.65	$48.60
Purchase #5	$55.33	11.544%	$61.7173	$61.72	$61.70	$61.70
Purchase #6	$97.58	3.326%	$100.8255	$100.83	$100.85	$100.80
Purchase #7	$103.46	9.684%	$113.4791	$113.48	$113.50	$113.50
7 purchase totals =	$504.41		$546.2323	$546.24	$546.25	$546.20