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	$210.63	7.208%	$225.8122	$225.81	$225.80	$225.80
Purchase #2	$189.97	9.633%	$208.2698	$208.27	$208.25	$208.30
Purchase #3	$88.42	4.570%	$92.4608	$92.46	$92.45	$92.50
Purchase #4	$196.33	9.749%	$215.4702	$215.47	$215.45	$215.50
Purchase #5	$84.49	13.473%	$95.8733	$95.87	$95.85	$95.90
Purchase #6	$12.46	3.551%	$12.9025	$12.90	$12.90	$12.90
Purchase #7	$12.55	9.654%	$13.7616	$13.76	$13.75	$13.80
7 purchase totals =	$794.85		$864.5504	$864.54	$864.45	$864.70