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	$236.66	8.353%	$256.4282	$256.43	$256.45	$256.40
Purchase #2	$162.89	11.380%	$181.4269	$181.43	$181.45	$181.40
Purchase #3	$144.62	6.656%	$154.2459	$154.25	$154.25	$154.20
Purchase #4	$246.55	13.829%	$280.6454	$280.65	$280.65	$280.60
Purchase #5	$117.73	12.123%	$132.0024	$132.00	$132.00	$132.00
Purchase #6	$35.28	6.228%	$37.4772	$37.48	$37.50	$37.50
Purchase #7	$77.64	7.602%	$83.5422	$83.54	$83.55	$83.50
7 purchase totals =	$1,021.37		$1,125.7682	$1,125.78	$1,125.85	$1,125.60