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	$246.26	4.273%	$256.7827	$256.78	$256.80	$256.80
Purchase #2	$154.37	4.701%	$161.6269	$161.63	$161.65	$161.60
Purchase #3	$65.56	9.566%	$71.8315	$71.83	$71.85	$71.80
Purchase #4	$116.87	12.622%	$131.6213	$131.62	$131.60	$131.60
Purchase #5	$81.38	5.489%	$85.8469	$85.85	$85.85	$85.80
Purchase #6	$217.89	4.570%	$227.8476	$227.85	$227.85	$227.80
Purchase #7	$62.81	6.821%	$67.0943	$67.09	$67.10	$67.10
7 purchase totals =	$945.14		$1,002.6512	$1,002.65	$1,002.70	$1,002.50