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	$64.34	4.207%	$67.0468	$67.05	$67.05	$67.00
Purchase #2	$133.47	8.370%	$144.6414	$144.64	$144.65	$144.60
Purchase #3	$242.82	5.278%	$255.636	$255.64	$255.65	$255.60
Purchase #4	$60.30	9.268%	$65.8886	$65.89	$65.90	$65.90
Purchase #5	$84.52	8.682%	$91.858	$91.86	$91.85	$91.90
Purchase #6	$233.76	10.408%	$258.0897	$258.09	$258.10	$258.10
Purchase #7	$56.64	6.639%	$60.4003	$60.40	$60.40	$60.40
7 purchase totals =	$875.85		$943.5608	$943.57	$943.60	$943.50