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	$115.75	12.726%	$130.4803	$130.48	$130.50	$130.50
Purchase #2	$109.54	12.675%	$123.4242	$123.42	$123.40	$123.40
Purchase #3	$172.60	9.849%	$189.5994	$189.60	$189.60	$189.60
Purchase #4	$95.34	5.379%	$100.4683	$100.47	$100.45	$100.50
Purchase #5	$221.36	6.688%	$236.1646	$236.16	$236.15	$236.20
Purchase #6	$124.31	10.800%	$137.7355	$137.74	$137.75	$137.70
Purchase #7	$94.86	7.181%	$101.6719	$101.67	$101.65	$101.70
7 purchase totals =	$933.76		$1,019.5442	$1,019.54	$1,019.50	$1,019.60