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	$241.50	7.582%	$259.8105	$259.81	$259.80	$259.80
Purchase #2	$9.54	5.292%	$10.0449	$10.04	$10.05	$10.00
Purchase #3	$54.45	12.518%	$61.2661	$61.27	$61.25	$61.30
Purchase #4	$163.31	6.217%	$173.463	$173.46	$173.45	$173.50
Purchase #5	$40.85	3.201%	$42.1576	$42.16	$42.15	$42.20
Purchase #6	$194.69	10.625%	$215.3758	$215.38	$215.40	$215.40
Purchase #7	$27.37	7.307%	$29.3699	$29.37	$29.35	$29.40
7 purchase totals =	$731.71		$791.4878	$791.49	$791.45	$791.60