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	$14.55	7.244%	$15.604	$15.60	$15.60	$15.60
Purchase #2	$246.90	10.201%	$272.0863	$272.09	$272.10	$272.10
Purchase #3	$18.59	3.662%	$19.2708	$19.27	$19.25	$19.30
Purchase #4	$227.39	12.436%	$255.6682	$255.67	$255.65	$255.70
Purchase #5	$100.73	4.636%	$105.3998	$105.40	$105.40	$105.40
Purchase #6	$201.83	5.112%	$212.1475	$212.15	$212.15	$212.10
Purchase #7	$233.81	12.685%	$263.4688	$263.47	$263.45	$263.50
7 purchase totals =	$1,043.80		$1,143.6454	$1,143.65	$1,143.60	$1,143.70