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	$90.28	11.803%	$100.9357	$100.94	$100.95	$100.90
Purchase #2	$169.60	10.610%	$187.5946	$187.59	$187.60	$187.60
Purchase #3	$217.99	4.523%	$227.8497	$227.85	$227.85	$227.80
Purchase #4	$57.51	7.331%	$61.7261	$61.73	$61.75	$61.70
Purchase #5	$247.76	10.401%	$273.5295	$273.53	$273.55	$273.50
Purchase #6	$69.55	13.210%	$78.7376	$78.74	$78.75	$78.70
Purchase #7	$62.34	13.509%	$70.7615	$70.76	$70.75	$70.80
7 purchase totals =	$915.03		$1,001.1347	$1,001.14	$1,001.20	$1,001.00