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	$56.50	13.103%	$63.9032	$63.90	$63.90	$63.90
Purchase #2	$148.46	5.290%	$156.3135	$156.31	$156.30	$156.30
Purchase #3	$66.75	8.551%	$72.4578	$72.46	$72.45	$72.50
Purchase #4	$220.86	11.302%	$245.8216	$245.82	$245.80	$245.80
Purchase #5	$10.82	9.719%	$11.8716	$11.87	$11.85	$11.90
Purchase #6	$36.30	6.181%	$38.5437	$38.54	$38.55	$38.50
Purchase #7	$34.25	10.809%	$37.9521	$37.95	$37.95	$38.00
7 purchase totals =	$573.94		$626.8635	$626.85	$626.80	$626.90