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	$60.90	9.677%	$66.7933	$66.79	$66.80	$66.80
Purchase #2	$156.25	13.387%	$177.1672	$177.17	$177.15	$177.20
Purchase #3	$244.78	8.454%	$265.4737	$265.47	$265.45	$265.50
Purchase #4	$211.83	8.125%	$229.0412	$229.04	$229.05	$229.00
Purchase #5	$84.69	6.507%	$90.2008	$90.20	$90.20	$90.20
Purchase #6	$64.49	12.509%	$72.5571	$72.56	$72.55	$72.60
Purchase #7	$106.82	7.453%	$114.7813	$114.78	$114.80	$114.80
7 purchase totals =	$929.76		$1,016.0146	$1,016.01	$1,016.00	$1,016.10