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	$110.67	7.154%	$118.5873	$118.59	$118.60	$118.60
Purchase #2	$246.67	3.277%	$254.7534	$254.75	$254.75	$254.80
Purchase #3	$46.47	10.816%	$51.4962	$51.50	$51.50	$51.50
Purchase #4	$38.46	11.448%	$42.8629	$42.86	$42.85	$42.90
Purchase #5	$11.38	4.549%	$11.8977	$11.90	$11.90	$11.90
Purchase #6	$236.99	8.275%	$256.6009	$256.60	$256.60	$256.60
Purchase #7	$15.71	9.167%	$17.1501	$17.15	$17.15	$17.20
7 purchase totals =	$706.35		$753.3485	$753.35	$753.35	$753.50