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	$106.68	4.441%	$111.4177	$111.42	$111.40	$111.40
Purchase #2	$152.97	13.650%	$173.8504	$173.85	$173.85	$173.90
Purchase #3	$174.40	5.416%	$183.8455	$183.85	$183.85	$183.80
Purchase #4	$65.49	10.836%	$72.5865	$72.59	$72.60	$72.60
Purchase #5	$103.67	8.817%	$112.8106	$112.81	$112.80	$112.80
Purchase #6	$100.38	3.614%	$104.0077	$104.01	$104.00	$104.00
Purchase #7	$219.53	12.556%	$247.0942	$247.09	$247.10	$247.10
7 purchase totals =	$923.12		$1,005.6126	$1,005.62	$1,005.60	$1,005.60