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	$52.69	7.441%	$56.6107	$56.61	$56.60	$56.60
Purchase #2	$42.27	3.835%	$43.8911	$43.89	$43.90	$43.90
Purchase #3	$107.86	5.559%	$113.8559	$113.86	$113.85	$113.90
Purchase #4	$177.50	10.741%	$196.5653	$196.57	$196.55	$196.60
Purchase #5	$162.43	13.159%	$183.8042	$183.80	$183.80	$183.80
Purchase #6	$206.96	8.638%	$224.8372	$224.84	$224.85	$224.80
Purchase #7	$123.39	13.641%	$140.2216	$140.22	$140.20	$140.20
7 purchase totals =	$873.10		$959.7860	$959.79	$959.75	$959.80