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	$81.86	13.220%	$92.6819	$92.68	$92.70	$92.70
Purchase #2	$59.45	7.420%	$63.8612	$63.86	$63.85	$63.90
Purchase #3	$99.39	12.149%	$111.4649	$111.46	$111.45	$111.50
Purchase #4	$82.43	6.368%	$87.6791	$87.68	$87.70	$87.70
Purchase #5	$148.79	6.770%	$158.8631	$158.86	$158.85	$158.90
Purchase #6	$122.52	7.847%	$132.1341	$132.13	$132.15	$132.10
Purchase #7	$148.89	7.656%	$160.289	$160.29	$160.30	$160.30
7 purchase totals =	$743.33		$806.9733	$806.96	$807.00	$807.10