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	$199.31	8.332%	$215.9165	$215.92	$215.90	$215.90
Purchase #2	$23.68	5.395%	$24.9575	$24.96	$24.95	$25.00
Purchase #3	$108.83	13.587%	$123.6167	$123.62	$123.60	$123.60
Purchase #4	$125.35	10.830%	$138.9254	$138.93	$138.95	$138.90
Purchase #5	$19.63	4.478%	$20.509	$20.51	$20.50	$20.50
Purchase #6	$105.75	5.492%	$111.5578	$111.56	$111.55	$111.60
Purchase #7	$203.25	7.677%	$218.8535	$218.85	$218.85	$218.90
7 purchase totals =	$785.80		$854.3364	$854.35	$854.30	$854.40