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	$238.56	6.607%	$254.3217	$254.32	$254.30	$254.30
Purchase #2	$40.95	6.490%	$43.6077	$43.61	$43.60	$43.60
Purchase #3	$34.43	3.466%	$35.6233	$35.62	$35.60	$35.60
Purchase #4	$114.91	10.638%	$127.1341	$127.13	$127.15	$127.10
Purchase #5	$120.72	4.526%	$126.1838	$126.18	$126.20	$126.20
Purchase #6	$245.77	6.783%	$262.4406	$262.44	$262.45	$262.40
Purchase #7	$34.72	3.756%	$36.0241	$36.02	$36.00	$36.00
7 purchase totals =	$830.06		$885.3353	$885.32	$885.30	$885.20