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	$95.63	5.133%	$100.5387	$100.54	$100.55	$100.50
Purchase #2	$31.40	4.475%	$32.8052	$32.81	$32.80	$32.80
Purchase #3	$9.28	10.254%	$10.2316	$10.23	$10.25	$10.20
Purchase #4	$24.31	3.108%	$25.0656	$25.07	$25.05	$25.10
Purchase #5	$102.78	11.556%	$114.6573	$114.66	$114.65	$114.70
Purchase #6	$210.84	3.202%	$217.5911	$217.59	$217.60	$217.60
Purchase #7	$217.89	10.791%	$241.4025	$241.40	$241.40	$241.40
7 purchase totals =	$692.13		$742.2920	$742.30	$742.30	$742.30