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	$179.78	12.161%	$201.643	$201.64	$201.65	$201.60
Purchase #2	$30.31	5.682%	$32.0322	$32.03	$32.05	$32.00
Purchase #3	$103.46	13.540%	$117.4685	$117.47	$117.45	$117.50
Purchase #4	$13.47	10.123%	$14.8336	$14.83	$14.85	$14.80
Purchase #5	$12.86	11.704%	$14.3651	$14.37	$14.35	$14.40
Purchase #6	$37.83	13.457%	$42.9208	$42.92	$42.90	$42.90
Purchase #7	$244.77	5.719%	$258.7684	$258.77	$258.75	$258.80
7 purchase totals =	$622.48		$682.0316	$682.03	$682.00	$682.00