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	$107.30	5.759%	$113.4794	$113.48	$113.50	$113.50
Purchase #2	$45.90	13.606%	$52.1452	$52.15	$52.15	$52.10
Purchase #3	$89.61	5.382%	$94.4328	$94.43	$94.45	$94.40
Purchase #4	$91.71	9.757%	$100.6581	$100.66	$100.65	$100.70
Purchase #5	$105.86	3.251%	$109.3015	$109.30	$109.30	$109.30
Purchase #6	$30.39	13.105%	$34.3726	$34.37	$34.35	$34.40
Purchase #7	$168.82	5.479%	$178.0696	$178.07	$178.05	$178.10
7 purchase totals =	$639.59		$682.4592	$682.46	$682.45	$682.50