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	$228.37	11.828%	$255.3816	$255.38	$255.40	$255.40
Purchase #2	$225.66	3.505%	$233.5694	$233.57	$233.55	$233.60
Purchase #3	$127.50	13.840%	$145.146	$145.15	$145.15	$145.10
Purchase #4	$32.77	11.661%	$36.5913	$36.59	$36.60	$36.60
Purchase #5	$152.30	13.814%	$173.3387	$173.34	$173.35	$173.30
Purchase #6	$208.36	11.870%	$233.0923	$233.09	$233.10	$233.10
Purchase #7	$250.77	11.127%	$278.6732	$278.67	$278.65	$278.70
7 purchase totals =	$1,225.73		$1,355.7925	$1,355.79	$1,355.80	$1,355.80