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	$23.60	6.206%	$25.0646	$25.06	$25.05	$25.10
Purchase #2	$105.59	4.178%	$110.0016	$110.00	$110.00	$110.00
Purchase #3	$88.92	12.862%	$100.3569	$100.36	$100.35	$100.40
Purchase #4	$113.79	6.871%	$121.6085	$121.61	$121.60	$121.60
Purchase #5	$49.31	11.171%	$54.8184	$54.82	$54.80	$54.80
Purchase #6	$126.80	11.828%	$141.7979	$141.80	$141.80	$141.80
Purchase #7	$63.89	13.346%	$72.4168	$72.42	$72.40	$72.40
7 purchase totals =	$571.90		$626.0647	$626.07	$626.00	$626.10