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	$44.90	8.538%	$48.7336	$48.73	$48.75	$48.70
Purchase #2	$193.95	3.388%	$200.521	$200.52	$200.50	$200.50
Purchase #3	$59.92	13.746%	$68.1566	$68.16	$68.15	$68.20
Purchase #4	$143.60	10.630%	$158.8647	$158.86	$158.85	$158.90
Purchase #5	$134.71	5.180%	$141.688	$141.69	$141.70	$141.70
Purchase #6	$116.27	5.845%	$123.066	$123.07	$123.05	$123.10
Purchase #7	$211.38	3.504%	$218.7868	$218.79	$218.80	$218.80
7 purchase totals =	$904.73		$959.8167	$959.82	$959.80	$959.90