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	$235.44	12.817%	$265.6163	$265.62	$265.60	$265.60
Purchase #2	$201.89	12.734%	$227.5987	$227.60	$227.60	$227.60
Purchase #3	$247.77	13.236%	$280.5648	$280.56	$280.55	$280.60
Purchase #4	$89.78	10.644%	$99.3362	$99.34	$99.35	$99.30
Purchase #5	$63.67	5.472%	$67.154	$67.15	$67.15	$67.20
Purchase #6	$117.61	13.469%	$133.4509	$133.45	$133.45	$133.50
Purchase #7	$177.59	8.647%	$192.9462	$192.95	$192.95	$192.90
7 purchase totals =	$1,133.75		$1,266.6671	$1,266.67	$1,266.65	$1,266.70