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	$126.64	7.795%	$136.5116	$136.51	$136.50	$136.50
Purchase #2	$168.38	9.193%	$183.8592	$183.86	$183.85	$183.90
Purchase #3	$90.73	5.771%	$95.966	$95.97	$95.95	$96.00
Purchase #4	$175.99	11.623%	$196.4453	$196.45	$196.45	$196.40
Purchase #5	$127.42	13.461%	$144.572	$144.57	$144.55	$144.60
Purchase #6	$157.83	13.113%	$178.5262	$178.53	$178.55	$178.50
Purchase #7	$221.72	11.826%	$247.9406	$247.94	$247.95	$247.90
7 purchase totals =	$1,068.71		$1,183.8209	$1,183.83	$1,183.80	$1,183.80