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	$59.27	6.334%	$63.0242	$63.02	$63.00	$63.00
Purchase #2	$93.89	8.491%	$101.8622	$101.86	$101.85	$101.90
Purchase #3	$100.26	6.658%	$106.9353	$106.94	$106.95	$106.90
Purchase #4	$39.91	9.534%	$43.715	$43.72	$43.70	$43.70
Purchase #5	$126.86	11.331%	$141.2345	$141.23	$141.25	$141.20
Purchase #6	$50.89	12.630%	$57.3174	$57.32	$57.30	$57.30
Purchase #7	$88.86	12.601%	$100.0572	$100.06	$100.05	$100.10
7 purchase totals =	$559.94		$614.1458	$614.15	$614.10	$614.10