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	$58.75	12.105%	$65.8617	$65.86	$65.85	$65.90
Purchase #2	$230.73	4.831%	$241.8766	$241.88	$241.90	$241.90
Purchase #3	$132.25	6.374%	$140.6796	$140.68	$140.70	$140.70
Purchase #4	$106.54	4.845%	$111.7019	$111.70	$111.70	$111.70
Purchase #5	$39.78	5.307%	$41.8911	$41.89	$41.90	$41.90
Purchase #6	$169.39	9.671%	$185.7717	$185.77	$185.75	$185.80
Purchase #7	$86.49	8.672%	$93.9904	$93.99	$94.00	$94.00
7 purchase totals =	$823.93		$881.7730	$881.77	$881.80	$881.90