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	$238.58	7.160%	$255.6623	$255.66	$255.65	$255.70
Purchase #2	$234.93	12.615%	$264.5664	$264.57	$264.55	$264.60
Purchase #3	$227.77	4.503%	$238.0265	$238.03	$238.05	$238.00
Purchase #4	$118.83	8.215%	$128.5919	$128.59	$128.60	$128.60
Purchase #5	$247.57	13.256%	$280.3879	$280.39	$280.40	$280.40
Purchase #6	$118.83	6.679%	$126.7667	$126.77	$126.75	$126.80
Purchase #7	$73.91	6.444%	$78.6728	$78.67	$78.65	$78.70
7 purchase totals =	$1,260.42		$1,372.6745	$1,372.68	$1,372.65	$1,372.80