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	$237.78	9.170%	$259.5844	$259.58	$259.60	$259.60
Purchase #2	$139.42	6.322%	$148.2341	$148.23	$148.25	$148.20
Purchase #3	$35.53	5.710%	$37.5588	$37.56	$37.55	$37.60
Purchase #4	$169.95	9.509%	$186.1105	$186.11	$186.10	$186.10
Purchase #5	$18.82	3.828%	$19.5404	$19.54	$19.55	$19.50
Purchase #6	$102.48	11.632%	$114.4005	$114.40	$114.40	$114.40
Purchase #7	$248.94	12.669%	$280.4782	$280.48	$280.50	$280.50
7 purchase totals =	$952.92		$1,045.9069	$1,045.90	$1,045.95	$1,045.90