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	$139.45	4.342%	$145.5049	$145.50	$145.50	$145.50
Purchase #2	$12.30	10.762%	$13.6237	$13.62	$13.60	$13.60
Purchase #3	$248.75	7.162%	$266.5655	$266.57	$266.55	$266.60
Purchase #4	$63.89	10.298%	$70.4694	$70.47	$70.45	$70.50
Purchase #5	$64.81	4.362%	$67.637	$67.64	$67.65	$67.60
Purchase #6	$11.57	12.628%	$13.0311	$13.03	$13.05	$13.00
Purchase #7	$198.26	10.832%	$219.7355	$219.74	$219.75	$219.70
7 purchase totals =	$739.03		$796.5671	$796.57	$796.55	$796.50