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	$33.26	13.382%	$37.7109	$37.71	$37.70	$37.70
Purchase #2	$82.31	3.308%	$85.0328	$85.03	$85.05	$85.00
Purchase #3	$105.73	10.536%	$116.8697	$116.87	$116.85	$116.90
Purchase #4	$41.63	3.500%	$43.0871	$43.09	$43.10	$43.10
Purchase #5	$40.32	8.439%	$43.7226	$43.72	$43.70	$43.70
Purchase #6	$108.45	13.282%	$122.8543	$122.85	$122.85	$122.90
Purchase #7	$48.45	11.499%	$54.0213	$54.02	$54.00	$54.00
7 purchase totals =	$460.15		$503.2987	$503.29	$503.25	$503.30