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	$238.93	10.390%	$263.7548	$263.75	$263.75	$263.80
Purchase #2	$12.87	4.780%	$13.4852	$13.49	$13.50	$13.50
Purchase #3	$39.88	5.768%	$42.1803	$42.18	$42.20	$42.20
Purchase #4	$170.54	9.548%	$186.8232	$186.82	$186.80	$186.80
Purchase #5	$146.30	3.271%	$151.0855	$151.09	$151.10	$151.10
Purchase #6	$110.67	11.668%	$123.583	$123.58	$123.60	$123.60
Purchase #7	$157.65	8.207%	$170.5883	$170.59	$170.60	$170.60
7 purchase totals =	$876.84		$951.5003	$951.50	$951.55	$951.60