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	$214.81	11.267%	$239.0126	$239.01	$239.00	$239.00
Purchase #2	$22.70	13.728%	$25.8163	$25.82	$25.80	$25.80
Purchase #3	$66.46	9.252%	$72.6089	$72.61	$72.60	$72.60
Purchase #4	$35.89	3.245%	$37.0546	$37.05	$37.05	$37.10
Purchase #5	$72.31	5.849%	$76.5394	$76.54	$76.55	$76.50
Purchase #6	$221.83	3.434%	$229.4476	$229.45	$229.45	$229.40
Purchase #7	$246.38	12.245%	$276.5492	$276.55	$276.55	$276.50
7 purchase totals =	$880.38		$957.0286	$957.03	$957.00	$956.90