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	$244.39	4.655%	$255.7664	$255.77	$255.75	$255.80
Purchase #2	$106.56	3.499%	$110.2885	$110.29	$110.30	$110.30
Purchase #3	$112.42	3.731%	$116.6144	$116.61	$116.60	$116.60
Purchase #4	$30.49	4.417%	$31.8367	$31.84	$31.85	$31.80
Purchase #5	$28.81	7.636%	$31.0099	$31.01	$31.00	$31.00
Purchase #6	$52.54	4.337%	$54.8187	$54.82	$54.80	$54.80
Purchase #7	$104.97	11.144%	$116.6679	$116.67	$116.65	$116.70
7 purchase totals =	$680.18		$717.0025	$717.01	$716.95	$717.00