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	$63.72	3.721%	$66.091	$66.09	$66.10	$66.10
Purchase #2	$221.42	9.563%	$242.5944	$242.59	$242.60	$242.60
Purchase #3	$142.30	7.767%	$153.3524	$153.35	$153.35	$153.40
Purchase #4	$148.99	8.444%	$161.5707	$161.57	$161.55	$161.60
Purchase #5	$136.77	3.187%	$141.1289	$141.13	$141.15	$141.10
Purchase #6	$90.65	13.464%	$102.8551	$102.86	$102.85	$102.90
Purchase #7	$134.72	6.798%	$143.8783	$143.88	$143.90	$143.90
7 purchase totals =	$938.57		$1,011.4708	$1,011.47	$1,011.50	$1,011.60