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	$96.64	7.283%	$103.6783	$103.68	$103.70	$103.70
Purchase #2	$94.52	6.509%	$100.6723	$100.67	$100.65	$100.70
Purchase #3	$100.59	7.524%	$108.1584	$108.16	$108.15	$108.20
Purchase #4	$148.47	9.545%	$162.6415	$162.64	$162.65	$162.60
Purchase #5	$66.65	4.602%	$69.7172	$69.72	$69.70	$69.70
Purchase #6	$82.53	9.872%	$90.6774	$90.68	$90.70	$90.70
Purchase #7	$168.78	4.207%	$175.8806	$175.88	$175.90	$175.90
7 purchase totals =	$758.18		$811.4257	$811.43	$811.45	$811.50