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	$214.65	3.338%	$221.815	$221.82	$221.80	$221.80
Purchase #2	$85.60	4.147%	$89.1498	$89.15	$89.15	$89.10
Purchase #3	$235.68	6.288%	$250.4996	$250.50	$250.50	$250.50
Purchase #4	$244.57	10.594%	$270.4797	$270.48	$270.50	$270.50
Purchase #5	$68.34	12.410%	$76.821	$76.82	$76.80	$76.80
Purchase #6	$126.83	5.693%	$134.0504	$134.05	$134.05	$134.10
Purchase #7	$12.29	9.102%	$13.4086	$13.41	$13.40	$13.40
7 purchase totals =	$987.96		$1,056.2241	$1,056.23	$1,056.20	$1,056.20