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	$146.34	9.627%	$160.4282	$160.43	$160.45	$160.40
Purchase #2	$29.63	4.102%	$30.8454	$30.85	$30.85	$30.80
Purchase #3	$144.61	13.808%	$164.5777	$164.58	$164.60	$164.60
Purchase #4	$48.81	4.129%	$50.8254	$50.83	$50.85	$50.80
Purchase #5	$174.26	7.821%	$187.8889	$187.89	$187.90	$187.90
Purchase #6	$67.44	7.477%	$72.4825	$72.48	$72.50	$72.50
Purchase #7	$110.31	5.286%	$116.141	$116.14	$116.15	$116.10
7 purchase totals =	$721.40		$783.1891	$783.20	$783.30	$783.10