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	$11.67	13.301%	$13.2222	$13.22	$13.20	$13.20
Purchase #2	$11.47	11.534%	$12.7929	$12.79	$12.80	$12.80
Purchase #3	$80.60	4.467%	$84.2004	$84.20	$84.20	$84.20
Purchase #4	$127.80	10.734%	$141.5181	$141.52	$141.50	$141.50
Purchase #5	$200.38	11.503%	$223.4297	$223.43	$223.45	$223.40
Purchase #6	$133.33	4.569%	$139.4218	$139.42	$139.40	$139.40
Purchase #7	$143.81	4.478%	$150.2498	$150.25	$150.25	$150.20
7 purchase totals =	$709.06		$764.8349	$764.83	$764.80	$764.70