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	$65.78	10.164%	$72.4659	$72.47	$72.45	$72.50
Purchase #2	$136.87	4.795%	$143.4329	$143.43	$143.45	$143.40
Purchase #3	$28.34	3.257%	$29.263	$29.26	$29.25	$29.30
Purchase #4	$78.99	3.568%	$81.8084	$81.81	$81.80	$81.80
Purchase #5	$204.45	12.652%	$230.317	$230.32	$230.30	$230.30
Purchase #6	$46.32	3.689%	$48.0287	$48.03	$48.05	$48.00
Purchase #7	$75.82	6.275%	$80.5777	$80.58	$80.60	$80.60
7 purchase totals =	$636.57		$685.8936	$685.90	$685.90	$685.90