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	$118.45	7.106%	$126.8671	$126.87	$126.85	$126.90
Purchase #2	$94.37	11.304%	$105.0376	$105.04	$105.05	$105.00
Purchase #3	$237.72	10.398%	$262.4381	$262.44	$262.45	$262.40
Purchase #4	$139.68	4.284%	$145.6639	$145.66	$145.65	$145.70
Purchase #5	$19.40	10.276%	$21.3935	$21.39	$21.40	$21.40
Purchase #6	$132.83	6.259%	$141.1438	$141.14	$141.15	$141.10
Purchase #7	$42.32	11.599%	$47.2287	$47.23	$47.25	$47.20
7 purchase totals =	$784.77		$849.7727	$849.77	$849.80	$849.70