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	$181.48	4.709%	$190.0259	$190.03	$190.05	$190.00
Purchase #2	$148.48	13.454%	$168.4565	$168.46	$168.45	$168.50
Purchase #3	$76.66	7.574%	$82.4662	$82.47	$82.45	$82.50
Purchase #4	$119.76	6.738%	$127.8294	$127.83	$127.85	$127.80
Purchase #5	$167.26	13.316%	$189.5323	$189.53	$189.55	$189.50
Purchase #6	$171.27	13.835%	$194.9652	$194.97	$194.95	$195.00
Purchase #7	$19.59	10.509%	$21.6487	$21.65	$21.65	$21.60
7 purchase totals =	$884.50		$974.9242	$974.94	$974.95	$974.90