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	$58.49	8.642%	$63.5447	$63.54	$63.55	$63.50
Purchase #2	$213.34	6.847%	$227.9474	$227.95	$227.95	$227.90
Purchase #3	$226.87	12.861%	$256.0478	$256.05	$256.05	$256.00
Purchase #4	$158.52	6.679%	$169.1076	$169.11	$169.10	$169.10
Purchase #5	$227.58	11.869%	$254.5915	$254.59	$254.60	$254.60
Purchase #6	$34.85	3.564%	$36.0921	$36.09	$36.10	$36.10
Purchase #7	$82.51	12.447%	$92.78	$92.78	$92.80	$92.80
7 purchase totals =	$1,002.16		$1,100.1111	$1,100.11	$1,100.15	$1,100.00