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	$112.56	7.349%	$120.832	$120.83	$120.85	$120.80
Purchase #2	$171.72	5.142%	$180.5498	$180.55	$180.55	$180.50
Purchase #3	$7.57	9.433%	$8.2841	$8.28	$8.30	$8.30
Purchase #4	$90.60	8.671%	$98.4559	$98.46	$98.45	$98.50
Purchase #5	$158.57	12.558%	$178.4832	$178.48	$178.50	$178.50
Purchase #6	$94.76	6.128%	$100.5669	$100.57	$100.55	$100.60
Purchase #7	$34.39	10.528%	$38.0106	$38.01	$38.00	$38.00
7 purchase totals =	$670.17		$725.1825	$725.18	$725.20	$725.20