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	$244.49	10.375%	$269.8558	$269.86	$269.85	$269.90
Purchase #2	$54.83	3.512%	$56.7556	$56.76	$56.75	$56.80
Purchase #3	$136.76	4.509%	$142.9265	$142.93	$142.95	$142.90
Purchase #4	$97.59	3.375%	$100.8837	$100.88	$100.90	$100.90
Purchase #5	$92.70	3.130%	$95.6015	$95.60	$95.60	$95.60
Purchase #6	$204.52	13.475%	$232.0791	$232.08	$232.10	$232.10
Purchase #7	$128.59	8.578%	$139.6205	$139.62	$139.60	$139.60
7 purchase totals =	$959.48		$1,037.7227	$1,037.73	$1,037.75	$1,037.80