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	$249.83	4.859%	$261.9692	$261.97	$261.95	$262.00
Purchase #2	$237.29	7.687%	$255.5305	$255.53	$255.55	$255.50
Purchase #3	$39.64	5.587%	$41.8547	$41.85	$41.85	$41.90
Purchase #4	$10.56	12.658%	$11.8967	$11.90	$11.90	$11.90
Purchase #5	$202.80	9.855%	$222.7859	$222.79	$222.80	$222.80
Purchase #6	$114.98	11.722%	$128.458	$128.46	$128.45	$128.50
Purchase #7	$81.77	11.134%	$90.8743	$90.87	$90.85	$90.90
7 purchase totals =	$936.87		$1,013.3693	$1,013.37	$1,013.35	$1,013.50