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	$211.54	9.213%	$231.0292	$231.03	$231.05	$231.00
Purchase #2	$198.89	9.451%	$217.6871	$217.69	$217.70	$217.70
Purchase #3	$131.50	9.831%	$144.4278	$144.43	$144.45	$144.40
Purchase #4	$132.83	3.334%	$137.2586	$137.26	$137.25	$137.30
Purchase #5	$217.51	12.550%	$244.8075	$244.81	$244.80	$244.80
Purchase #6	$54.75	9.378%	$59.8845	$59.88	$59.90	$59.90
Purchase #7	$68.95	13.207%	$78.0562	$78.06	$78.05	$78.10
7 purchase totals =	$1,015.97		$1,113.1509	$1,113.16	$1,113.20	$1,113.20