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	$250.56	4.845%	$262.6996	$262.70	$262.70	$262.70
Purchase #2	$222.74	11.230%	$247.7537	$247.75	$247.75	$247.80
Purchase #3	$148.68	5.538%	$156.9139	$156.91	$156.90	$156.90
Purchase #4	$61.42	4.364%	$64.1004	$64.10	$64.10	$64.10
Purchase #5	$75.98	6.626%	$81.0144	$81.01	$81.00	$81.00
Purchase #6	$146.81	8.715%	$159.6045	$159.60	$159.60	$159.60
Purchase #7	$42.87	6.792%	$45.7817	$45.78	$45.80	$45.80
7 purchase totals =	$949.06		$1,017.8682	$1,017.85	$1,017.85	$1,017.90