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	$153.94	6.736%	$164.3094	$164.31	$164.30	$164.30
Purchase #2	$54.47	5.726%	$57.589	$57.59	$57.60	$57.60
Purchase #3	$226.36	5.458%	$238.7147	$238.71	$238.70	$238.70
Purchase #4	$124.50	11.653%	$139.008	$139.01	$139.00	$139.00
Purchase #5	$30.84	3.203%	$31.8278	$31.83	$31.85	$31.80
Purchase #6	$76.92	8.551%	$83.4974	$83.50	$83.50	$83.50
Purchase #7	$129.50	12.483%	$145.6655	$145.67	$145.65	$145.70
7 purchase totals =	$796.53		$860.6118	$860.62	$860.60	$860.60