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	$138.39	8.758%	$150.5102	$150.51	$150.50	$150.50
Purchase #2	$145.46	9.169%	$158.7972	$158.80	$158.80	$158.80
Purchase #3	$52.83	13.688%	$60.0614	$60.06	$60.05	$60.10
Purchase #4	$126.97	12.408%	$142.7244	$142.72	$142.70	$142.70
Purchase #5	$172.47	13.855%	$196.3657	$196.37	$196.35	$196.40
Purchase #6	$225.51	4.571%	$235.8181	$235.82	$235.80	$235.80
Purchase #7	$145.26	5.616%	$153.4178	$153.42	$153.40	$153.40
7 purchase totals =	$1,006.89		$1,097.6948	$1,097.70	$1,097.60	$1,097.70