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	$84.84	13.870%	$96.6073	$96.61	$96.60	$96.60
Purchase #2	$10.29	6.749%	$10.9845	$10.98	$11.00	$11.00
Purchase #3	$173.72	11.756%	$194.1425	$194.14	$194.15	$194.10
Purchase #4	$19.64	4.551%	$20.5338	$20.53	$20.55	$20.50
Purchase #5	$38.26	13.816%	$43.546	$43.55	$43.55	$43.50
Purchase #6	$12.52	8.585%	$13.5948	$13.59	$13.60	$13.60
Purchase #7	$171.38	10.313%	$189.0544	$189.05	$189.05	$189.10
7 purchase totals =	$510.65		$568.4633	$568.45	$568.50	$568.40