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	$242.63	10.157%	$267.2739	$267.27	$267.25	$267.30
Purchase #2	$202.27	12.518%	$227.5902	$227.59	$227.60	$227.60
Purchase #3	$212.68	11.325%	$236.766	$236.77	$236.75	$236.80
Purchase #4	$59.65	10.628%	$65.9896	$65.99	$66.00	$66.00
Purchase #5	$43.43	5.759%	$45.9311	$45.93	$45.95	$45.90
Purchase #6	$204.82	8.726%	$222.6926	$222.69	$222.70	$222.70
Purchase #7	$57.80	6.557%	$61.5899	$61.59	$61.60	$61.60
7 purchase totals =	$1,023.28		$1,127.8333	$1,127.83	$1,127.85	$1,127.90