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	$97.39	10.283%	$107.4046	$107.40	$107.40	$107.40
Purchase #2	$148.28	13.847%	$168.8123	$168.81	$168.80	$168.80
Purchase #3	$63.36	4.323%	$66.0991	$66.10	$66.10	$66.10
Purchase #4	$79.57	12.458%	$89.4828	$89.48	$89.50	$89.50
Purchase #5	$167.52	5.402%	$176.5694	$176.57	$176.55	$176.60
Purchase #6	$179.72	10.761%	$199.0597	$199.06	$199.05	$199.10
Purchase #7	$205.73	4.246%	$214.4653	$214.47	$214.45	$214.50
7 purchase totals =	$941.57		$1,021.8932	$1,021.89	$1,021.85	$1,022.00