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	$29.50	8.709%	$32.0692	$32.07	$32.05	$32.10
Purchase #2	$120.79	13.190%	$136.7222	$136.72	$136.70	$136.70
Purchase #3	$83.70	8.410%	$90.7392	$90.74	$90.75	$90.70
Purchase #4	$49.83	13.870%	$56.7414	$56.74	$56.75	$56.70
Purchase #5	$174.39	9.450%	$190.8699	$190.87	$190.85	$190.90
Purchase #6	$21.57	10.128%	$23.7546	$23.75	$23.75	$23.80
Purchase #7	$226.56	6.564%	$241.4314	$241.43	$241.45	$241.40
7 purchase totals =	$706.34		$772.3279	$772.32	$772.30	$772.30