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	$17.48	12.213%	$19.6148	$19.61	$19.60	$19.60
Purchase #2	$101.72	5.705%	$107.5231	$107.52	$107.50	$107.50
Purchase #3	$84.40	7.162%	$90.4447	$90.44	$90.45	$90.40
Purchase #4	$42.26	8.398%	$45.809	$45.81	$45.80	$45.80
Purchase #5	$205.69	13.172%	$232.7835	$232.78	$232.80	$232.80
Purchase #6	$212.44	4.799%	$222.635	$222.64	$222.65	$222.60
Purchase #7	$225.87	13.631%	$256.6583	$256.66	$256.65	$256.70
7 purchase totals =	$889.86		$975.4684	$975.46	$975.45	$975.40