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	$209.37	8.715%	$227.6166	$227.62	$227.60	$227.60
Purchase #2	$189.66	3.371%	$196.0534	$196.05	$196.05	$196.10
Purchase #3	$51.93	4.788%	$54.4164	$54.42	$54.40	$54.40
Purchase #4	$163.97	4.742%	$171.7455	$171.75	$171.75	$171.70
Purchase #5	$83.92	13.237%	$95.0285	$95.03	$95.05	$95.00
Purchase #6	$97.77	11.821%	$109.3274	$109.33	$109.35	$109.30
Purchase #7	$136.27	7.670%	$146.7219	$146.72	$146.70	$146.70
7 purchase totals =	$932.89		$1,000.9097	$1,000.92	$1,000.90	$1,000.80