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	$219.42	11.511%	$244.6774	$244.68	$244.70	$244.70
Purchase #2	$87.81	9.268%	$95.9482	$95.95	$95.95	$95.90
Purchase #3	$99.83	11.558%	$111.3684	$111.37	$111.35	$111.40
Purchase #4	$60.39	7.647%	$65.008	$65.01	$65.00	$65.00
Purchase #5	$110.31	9.299%	$120.5677	$120.57	$120.55	$120.60
Purchase #6	$20.80	5.422%	$21.9278	$21.93	$21.95	$21.90
Purchase #7	$188.61	6.466%	$200.8055	$200.81	$200.80	$200.80
7 purchase totals =	$787.17		$860.3030	$860.32	$860.30	$860.30