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	$216.91	7.772%	$233.7682	$233.77	$233.75	$233.80
Purchase #2	$171.38	7.849%	$184.8316	$184.83	$184.85	$184.80
Purchase #3	$84.55	4.709%	$88.5315	$88.53	$88.55	$88.50
Purchase #4	$60.45	9.659%	$66.2889	$66.29	$66.30	$66.30
Purchase #5	$49.49	12.381%	$55.6174	$55.62	$55.60	$55.60
Purchase #6	$213.39	8.590%	$231.7202	$231.72	$231.70	$231.70
Purchase #7	$87.30	13.594%	$99.1676	$99.17	$99.15	$99.20
7 purchase totals =	$883.47		$959.9254	$959.93	$959.90	$959.90