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	$165.40	10.605%	$182.9407	$182.94	$182.95	$182.90
Purchase #2	$42.78	7.219%	$45.8683	$45.87	$45.85	$45.90
Purchase #3	$87.60	12.684%	$98.7112	$98.71	$98.70	$98.70
Purchase #4	$38.61	13.611%	$43.8652	$43.87	$43.85	$43.90
Purchase #5	$122.39	13.571%	$138.9995	$139.00	$139.00	$139.00
Purchase #6	$202.64	5.762%	$214.3161	$214.32	$214.30	$214.30
Purchase #7	$59.65	4.583%	$62.3838	$62.38	$62.40	$62.40
7 purchase totals =	$719.07		$787.0848	$787.09	$787.05	$787.10