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	$198.49	8.784%	$215.9254	$215.93	$215.95	$215.90
Purchase #2	$48.35	8.669%	$52.5415	$52.54	$52.55	$52.50
Purchase #3	$86.46	6.147%	$91.7747	$91.77	$91.75	$91.80
Purchase #4	$63.79	13.591%	$72.4597	$72.46	$72.45	$72.50
Purchase #5	$154.78	7.765%	$166.7987	$166.80	$166.80	$166.80
Purchase #6	$188.38	5.732%	$199.1779	$199.18	$199.20	$199.20
Purchase #7	$9.87	10.314%	$10.888	$10.89	$10.90	$10.90
7 purchase totals =	$750.12		$809.5659	$809.57	$809.60	$809.60