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	$126.79	13.311%	$143.667	$143.67	$143.65	$143.70
Purchase #2	$30.60	6.122%	$32.4733	$32.47	$32.45	$32.50
Purchase #3	$174.49	4.451%	$182.2565	$182.26	$182.25	$182.30
Purchase #4	$144.27	8.680%	$156.7926	$156.79	$156.80	$156.80
Purchase #5	$82.79	4.621%	$86.6157	$86.62	$86.60	$86.60
Purchase #6	$35.96	12.204%	$40.3486	$40.35	$40.35	$40.30
Purchase #7	$114.60	4.247%	$119.4671	$119.47	$119.45	$119.50
7 purchase totals =	$709.50		$761.6208	$761.63	$761.55	$761.70