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	$33.74	10.498%	$37.282	$37.28	$37.30	$37.30
Purchase #2	$55.69	7.509%	$59.8718	$59.87	$59.85	$59.90
Purchase #3	$146.53	4.235%	$152.7355	$152.74	$152.75	$152.70
Purchase #4	$121.65	13.268%	$137.7905	$137.79	$137.80	$137.80
Purchase #5	$87.56	13.161%	$99.0838	$99.08	$99.10	$99.10
Purchase #6	$241.27	10.495%	$266.5913	$266.59	$266.60	$266.60
Purchase #7	$80.85	7.789%	$87.1474	$87.15	$87.15	$87.10
7 purchase totals =	$767.29		$840.5023	$840.50	$840.55	$840.50