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	$80.34	3.206%	$82.9157	$82.92	$82.90	$82.90
Purchase #2	$131.82	5.343%	$138.8631	$138.86	$138.85	$138.90
Purchase #3	$104.52	11.472%	$116.5105	$116.51	$116.50	$116.50
Purchase #4	$161.94	3.677%	$167.8945	$167.89	$167.90	$167.90
Purchase #5	$214.85	8.490%	$233.0908	$233.09	$233.10	$233.10
Purchase #6	$48.71	5.412%	$51.3462	$51.35	$51.35	$51.30
Purchase #7	$193.31	4.756%	$202.5038	$202.50	$202.50	$202.50
7 purchase totals =	$935.49		$993.1246	$993.12	$993.10	$993.10