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	$137.82	9.351%	$150.7075	$150.71	$150.70	$150.70
Purchase #2	$74.69	4.340%	$77.9315	$77.93	$77.95	$77.90
Purchase #3	$108.80	4.723%	$113.9386	$113.94	$113.95	$113.90
Purchase #4	$200.48	12.521%	$225.5821	$225.58	$225.60	$225.60
Purchase #5	$103.27	12.778%	$116.4658	$116.47	$116.45	$116.50
Purchase #6	$229.41	4.707%	$240.2083	$240.21	$240.20	$240.20
Purchase #7	$17.59	5.677%	$18.5886	$18.59	$18.60	$18.60
7 purchase totals =	$872.06		$943.4224	$943.43	$943.45	$943.40