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	$125.66	13.735%	$142.9194	$142.92	$142.90	$142.90
Purchase #2	$248.90	7.451%	$267.4455	$267.45	$267.45	$267.40
Purchase #3	$159.50	6.129%	$169.2758	$169.28	$169.30	$169.30
Purchase #4	$99.28	12.646%	$111.8349	$111.83	$111.85	$111.80
Purchase #5	$151.49	6.427%	$161.2263	$161.23	$161.25	$161.20
Purchase #6	$44.25	3.518%	$45.8067	$45.81	$45.80	$45.80
Purchase #7	$39.82	11.723%	$44.4881	$44.49	$44.50	$44.50
7 purchase totals =	$868.90		$942.9967	$943.01	$943.05	$942.90