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	$229.63	11.749%	$256.6092	$256.61	$256.60	$256.60
Purchase #2	$13.65	11.679%	$15.2442	$15.24	$15.25	$15.20
Purchase #3	$218.49	3.387%	$225.8903	$225.89	$225.90	$225.90
Purchase #4	$113.64	5.492%	$119.8811	$119.88	$119.90	$119.90
Purchase #5	$18.62	10.303%	$20.5384	$20.54	$20.55	$20.50
Purchase #6	$86.45	8.707%	$93.9772	$93.98	$94.00	$94.00
Purchase #7	$108.31	11.149%	$120.3855	$120.39	$120.40	$120.40
7 purchase totals =	$788.79		$852.5259	$852.53	$852.60	$852.50