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	$229.38	11.503%	$255.7656	$255.77	$255.75	$255.80
Purchase #2	$64.81	12.305%	$72.7849	$72.78	$72.80	$72.80
Purchase #3	$172.55	11.757%	$192.8367	$192.84	$192.85	$192.80
Purchase #4	$59.35	13.862%	$67.5771	$67.58	$67.60	$67.60
Purchase #5	$145.32	10.153%	$160.0743	$160.07	$160.05	$160.10
Purchase #6	$135.44	5.173%	$142.4463	$142.45	$142.45	$142.40
Purchase #7	$228.72	10.184%	$252.0128	$252.01	$252.00	$252.00
7 purchase totals =	$1,035.57		$1,143.4977	$1,143.50	$1,143.50	$1,143.50