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	$126.61	5.735%	$133.8711	$133.87	$133.85	$133.90
Purchase #2	$246.72	13.665%	$280.4343	$280.43	$280.45	$280.40
Purchase #3	$71.99	6.594%	$76.737	$76.74	$76.75	$76.70
Purchase #4	$213.97	6.520%	$227.9208	$227.92	$227.90	$227.90
Purchase #5	$23.31	7.228%	$24.9948	$24.99	$25.00	$25.00
Purchase #6	$182.72	7.345%	$196.1408	$196.14	$196.15	$196.10
Purchase #7	$132.58	10.714%	$146.7846	$146.78	$146.80	$146.80
7 purchase totals =	$997.90		$1,086.8834	$1,086.87	$1,086.90	$1,086.80