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	$65.50	11.276%	$72.8858	$72.89	$72.90	$72.90
Purchase #2	$231.87	10.667%	$256.6036	$256.60	$256.60	$256.60
Purchase #3	$7.72	7.158%	$8.2726	$8.27	$8.25	$8.30
Purchase #4	$46.79	10.706%	$51.7993	$51.80	$51.80	$51.80
Purchase #5	$38.26	10.748%	$42.3722	$42.37	$42.35	$42.40
Purchase #6	$239.59	8.324%	$259.5335	$259.53	$259.55	$259.50
Purchase #7	$163.54	11.171%	$181.8091	$181.81	$181.80	$181.80
7 purchase totals =	$793.27		$873.2761	$873.27	$873.25	$873.30