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	$74.41	10.811%	$82.4545	$82.45	$82.45	$82.50
Purchase #2	$118.83	10.452%	$131.2501	$131.25	$131.25	$131.30
Purchase #3	$105.77	10.517%	$116.8938	$116.89	$116.90	$116.90
Purchase #4	$147.65	6.818%	$157.7168	$157.72	$157.70	$157.70
Purchase #5	$92.64	5.273%	$97.5249	$97.52	$97.50	$97.50
Purchase #6	$45.89	8.657%	$49.8627	$49.86	$49.85	$49.90
Purchase #7	$190.34	11.749%	$212.703	$212.70	$212.70	$212.70
7 purchase totals =	$775.53		$848.4058	$848.39	$848.35	$848.50