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	$46.85	10.843%	$51.9299	$51.93	$51.95	$51.90
Purchase #2	$224.83	12.314%	$252.5156	$252.52	$252.50	$252.50
Purchase #3	$155.64	12.365%	$174.8849	$174.88	$174.90	$174.90
Purchase #4	$90.80	13.281%	$102.8591	$102.86	$102.85	$102.90
Purchase #5	$100.76	7.591%	$108.4087	$108.41	$108.40	$108.40
Purchase #6	$197.93	3.601%	$205.0575	$205.06	$205.05	$205.10
Purchase #7	$34.80	8.155%	$37.6379	$37.64	$37.65	$37.60
7 purchase totals =	$851.61		$933.2936	$933.30	$933.30	$933.30