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	$35.35	5.533%	$37.3059	$37.31	$37.30	$37.30
Purchase #2	$48.68	3.701%	$50.4816	$50.48	$50.50	$50.50
Purchase #3	$242.60	7.156%	$259.9605	$259.96	$259.95	$260.00
Purchase #4	$59.65	6.373%	$63.4515	$63.45	$63.45	$63.50
Purchase #5	$155.58	10.559%	$172.0077	$172.01	$172.00	$172.00
Purchase #6	$26.66	4.504%	$27.8608	$27.86	$27.85	$27.90
Purchase #7	$141.29	12.340%	$158.7252	$158.73	$158.75	$158.70
7 purchase totals =	$709.81		$769.7932	$769.80	$769.80	$769.90