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	$184.68	6.551%	$196.7784	$196.78	$196.80	$196.80
Purchase #2	$138.81	12.713%	$156.4569	$156.46	$156.45	$156.50
Purchase #3	$195.38	12.604%	$220.0057	$220.01	$220.00	$220.00
Purchase #4	$124.46	3.499%	$128.8149	$128.81	$128.80	$128.80
Purchase #5	$55.95	13.838%	$63.6924	$63.69	$63.70	$63.70
Purchase #6	$236.51	8.383%	$256.3366	$256.34	$256.35	$256.30
Purchase #7	$173.49	12.113%	$194.5048	$194.50	$194.50	$194.50
7 purchase totals =	$1,109.28		$1,216.5897	$1,216.59	$1,216.60	$1,216.60