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	$97.52	11.108%	$108.3525	$108.35	$108.35	$108.40
Purchase #2	$48.48	13.158%	$54.859	$54.86	$54.85	$54.90
Purchase #3	$137.85	9.268%	$150.6259	$150.63	$150.65	$150.60
Purchase #4	$146.69	10.360%	$161.8871	$161.89	$161.90	$161.90
Purchase #5	$118.29	4.255%	$123.3232	$123.32	$123.30	$123.30
Purchase #6	$205.96	13.532%	$233.8305	$233.83	$233.85	$233.80
Purchase #7	$95.77	12.749%	$107.9797	$107.98	$108.00	$108.00
7 purchase totals =	$850.56		$940.8579	$940.86	$940.90	$940.90