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	$126.42	10.473%	$139.66	$139.66	$139.65	$139.70
Purchase #2	$62.71	12.435%	$70.508	$70.51	$70.50	$70.50
Purchase #3	$249.55	12.473%	$280.6764	$280.68	$280.70	$280.70
Purchase #4	$112.68	4.470%	$117.7168	$117.72	$117.70	$117.70
Purchase #5	$77.40	5.324%	$81.5208	$81.52	$81.50	$81.50
Purchase #6	$134.97	12.805%	$152.2529	$152.25	$152.25	$152.30
Purchase #7	$92.42	7.211%	$99.0844	$99.08	$99.10	$99.10
7 purchase totals =	$856.15		$941.4193	$941.42	$941.40	$941.50