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	$212.67	11.406%	$236.9271	$236.93	$236.95	$236.90
Purchase #2	$18.88	10.506%	$20.8635	$20.86	$20.85	$20.90
Purchase #3	$59.89	3.680%	$62.094	$62.09	$62.10	$62.10
Purchase #4	$102.81	7.577%	$110.5999	$110.60	$110.60	$110.60
Purchase #5	$212.86	4.108%	$221.6043	$221.60	$221.60	$221.60
Purchase #6	$58.55	11.767%	$65.4396	$65.44	$65.45	$65.40
Purchase #7	$136.93	4.688%	$143.3493	$143.35	$143.35	$143.30
7 purchase totals =	$802.59		$860.8777	$860.87	$860.90	$860.80