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	$250.38	6.414%	$266.4394	$266.44	$266.45	$266.40
Purchase #2	$123.99	3.127%	$127.8672	$127.87	$127.85	$127.90
Purchase #3	$200.51	8.671%	$217.8962	$217.90	$217.90	$217.90
Purchase #4	$99.64	8.207%	$107.8175	$107.82	$107.80	$107.80
Purchase #5	$144.74	10.770%	$160.3285	$160.33	$160.35	$160.30
Purchase #6	$99.33	4.302%	$103.6032	$103.60	$103.60	$103.60
Purchase #7	$43.58	13.837%	$49.6102	$49.61	$49.60	$49.60
7 purchase totals =	$962.17		$1,033.5622	$1,033.57	$1,033.55	$1,033.50