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	$134.47	12.633%	$151.4576	$151.46	$151.45	$151.50
Purchase #2	$217.60	12.526%	$244.8566	$244.86	$244.85	$244.90
Purchase #3	$13.87	10.400%	$15.3125	$15.31	$15.30	$15.30
Purchase #4	$154.80	11.589%	$172.7398	$172.74	$172.75	$172.70
Purchase #5	$46.36	13.561%	$52.6469	$52.65	$52.65	$52.60
Purchase #6	$36.35	6.730%	$38.7964	$38.80	$38.80	$38.80
Purchase #7	$211.94	4.849%	$222.217	$222.22	$222.20	$222.20
7 purchase totals =	$815.39		$898.0268	$898.04	$898.00	$898.00