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	$93.57	7.243%	$100.3473	$100.35	$100.35	$100.30
Purchase #2	$33.81	13.698%	$38.4413	$38.44	$38.45	$38.40
Purchase #3	$179.31	5.733%	$189.5898	$189.59	$189.60	$189.60
Purchase #4	$59.41	5.509%	$62.6829	$62.68	$62.70	$62.70
Purchase #5	$76.34	9.798%	$83.8198	$83.82	$83.80	$83.80
Purchase #6	$105.58	11.167%	$117.3701	$117.37	$117.35	$117.40
Purchase #7	$56.43	6.357%	$60.0173	$60.02	$60.00	$60.00
7 purchase totals =	$604.45		$652.2685	$652.27	$652.25	$652.20