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	$60.43	5.474%	$63.7379	$63.74	$63.75	$63.70
Purchase #2	$47.59	12.610%	$53.5911	$53.59	$53.60	$53.60
Purchase #3	$175.84	13.720%	$199.9652	$199.97	$199.95	$200.00
Purchase #4	$48.34	8.260%	$52.3329	$52.33	$52.35	$52.30
Purchase #5	$81.25	3.278%	$83.9134	$83.91	$83.90	$83.90
Purchase #6	$40.95	4.839%	$42.9316	$42.93	$42.95	$42.90
Purchase #7	$78.63	10.456%	$86.8516	$86.85	$86.85	$86.90
7 purchase totals =	$533.03		$583.3237	$583.32	$583.35	$583.30