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	$196.56	13.383%	$222.8656	$222.87	$222.85	$222.90
Purchase #2	$10.65	7.388%	$11.4368	$11.44	$11.45	$11.40
Purchase #3	$246.64	13.699%	$280.4272	$280.43	$280.45	$280.40
Purchase #4	$223.66	8.464%	$242.5906	$242.59	$242.60	$242.60
Purchase #5	$68.35	13.736%	$77.7386	$77.74	$77.75	$77.70
Purchase #6	$12.65	6.387%	$13.458	$13.46	$13.45	$13.50
Purchase #7	$68.68	13.779%	$78.1434	$78.14	$78.15	$78.10
7 purchase totals =	$827.19		$926.6602	$926.67	$926.70	$926.60