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	$190.83	13.851%	$217.2619	$217.26	$217.25	$217.30
Purchase #2	$101.78	10.219%	$112.1809	$112.18	$112.20	$112.20
Purchase #3	$40.81	11.692%	$45.5815	$45.58	$45.60	$45.60
Purchase #4	$68.98	13.436%	$78.2482	$78.25	$78.25	$78.20
Purchase #5	$116.52	7.689%	$125.4792	$125.48	$125.50	$125.50
Purchase #6	$221.93	5.181%	$233.4282	$233.43	$233.45	$233.40
Purchase #7	$109.61	8.452%	$118.8742	$118.87	$118.85	$118.90
7 purchase totals =	$850.46		$931.0541	$931.05	$931.10	$931.10