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	$55.78	3.429%	$57.6927	$57.69	$57.70	$57.70
Purchase #2	$137.37	13.298%	$155.6375	$155.64	$155.65	$155.60
Purchase #3	$108.45	10.122%	$119.4273	$119.43	$119.45	$119.40
Purchase #4	$85.48	8.562%	$92.7988	$92.80	$92.80	$92.80
Purchase #5	$230.71	3.197%	$238.0858	$238.09	$238.10	$238.10
Purchase #6	$136.44	4.733%	$142.8977	$142.90	$142.90	$142.90
Purchase #7	$191.35	4.512%	$199.9837	$199.98	$200.00	$200.00
7 purchase totals =	$945.58		$1,006.5235	$1,006.53	$1,006.60	$1,006.50