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	$209.71	4.462%	$219.0673	$219.07	$219.05	$219.10
Purchase #2	$39.96	13.281%	$45.2671	$45.27	$45.25	$45.30
Purchase #3	$176.30	8.268%	$190.8765	$190.88	$190.90	$190.90
Purchase #4	$97.85	6.155%	$103.8727	$103.87	$103.85	$103.90
Purchase #5	$246.45	13.151%	$278.8606	$278.86	$278.85	$278.90
Purchase #6	$208.38	11.230%	$231.7811	$231.78	$231.80	$231.80
Purchase #7	$35.60	12.201%	$39.9436	$39.94	$39.95	$39.90
7 purchase totals =	$1,014.25		$1,109.6689	$1,109.67	$1,109.65	$1,109.80