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	$171.83	11.693%	$191.9221	$191.92	$191.90	$191.90
Purchase #2	$65.88	13.558%	$74.812	$74.81	$74.80	$74.80
Purchase #3	$179.37	9.523%	$196.4514	$196.45	$196.45	$196.50
Purchase #4	$91.87	9.762%	$100.8383	$100.84	$100.85	$100.80
Purchase #5	$149.48	3.128%	$154.1557	$154.16	$154.15	$154.20
Purchase #6	$179.43	5.757%	$189.7598	$189.76	$189.75	$189.80
Purchase #7	$57.58	10.639%	$63.7059	$63.71	$63.70	$63.70
7 purchase totals =	$895.44		$971.6452	$971.65	$971.60	$971.70