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	$62.41	8.323%	$67.6044	$67.60	$67.60	$67.60
Purchase #2	$48.32	9.325%	$52.8258	$52.83	$52.85	$52.80
Purchase #3	$40.98	6.361%	$43.5867	$43.59	$43.60	$43.60
Purchase #4	$102.40	10.271%	$112.9175	$112.92	$112.90	$112.90
Purchase #5	$83.78	12.240%	$94.0347	$94.03	$94.05	$94.00
Purchase #6	$214.98	7.756%	$231.6538	$231.65	$231.65	$231.70
Purchase #7	$55.77	7.221%	$59.7972	$59.80	$59.80	$59.80
7 purchase totals =	$608.64		$662.4201	$662.42	$662.45	$662.40