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	$138.25	10.269%	$152.4469	$152.45	$152.45	$152.40
Purchase #2	$98.70	4.748%	$103.3863	$103.39	$103.40	$103.40
Purchase #3	$239.56	9.340%	$261.9349	$261.93	$261.95	$261.90
Purchase #4	$81.95	3.810%	$85.0723	$85.07	$85.05	$85.10
Purchase #5	$61.55	3.700%	$63.8274	$63.83	$63.85	$63.80
Purchase #6	$98.48	5.584%	$103.9791	$103.98	$104.00	$104.00
Purchase #7	$207.70	12.524%	$233.7123	$233.71	$233.70	$233.70
7 purchase totals =	$926.19		$1,004.3592	$1,004.36	$1,004.40	$1,004.30