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	$80.25	11.520%	$89.4948	$89.49	$89.50	$89.50
Purchase #2	$65.30	8.307%	$70.7245	$70.72	$70.70	$70.70
Purchase #3	$195.36	4.763%	$204.665	$204.67	$204.65	$204.70
Purchase #4	$195.77	12.394%	$220.0337	$220.03	$220.05	$220.00
Purchase #5	$150.81	5.740%	$159.4665	$159.47	$159.45	$159.50
Purchase #6	$64.60	11.844%	$72.2512	$72.25	$72.25	$72.30
Purchase #7	$49.72	4.383%	$51.8992	$51.90	$51.90	$51.90
7 purchase totals =	$801.81		$868.5349	$868.53	$868.50	$868.60