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	$225.81	9.196%	$246.5755	$246.58	$246.60	$246.60
Purchase #2	$226.90	9.304%	$248.0108	$248.01	$248.00	$248.00
Purchase #3	$115.65	13.750%	$131.5519	$131.55	$131.55	$131.60
Purchase #4	$90.52	5.202%	$95.2289	$95.23	$95.25	$95.20
Purchase #5	$102.31	3.491%	$105.8816	$105.88	$105.90	$105.90
Purchase #6	$104.61	13.534%	$118.7679	$118.77	$118.75	$118.80
Purchase #7	$221.28	7.763%	$238.458	$238.46	$238.45	$238.50
7 purchase totals =	$1,087.08		$1,184.4746	$1,184.48	$1,184.50	$1,184.60