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	$42.78	8.849%	$46.5656	$46.57	$46.55	$46.60
Purchase #2	$43.25	5.221%	$45.5081	$45.51	$45.50	$45.50
Purchase #3	$62.86	3.153%	$64.842	$64.84	$64.85	$64.80
Purchase #4	$48.48	11.262%	$53.9398	$53.94	$53.95	$53.90
Purchase #5	$32.49	5.269%	$34.2019	$34.20	$34.20	$34.20
Purchase #6	$237.67	10.407%	$262.4043	$262.40	$262.40	$262.40
Purchase #7	$127.32	5.475%	$134.2908	$134.29	$134.30	$134.30
7 purchase totals =	$594.85		$641.7525	$641.75	$641.75	$641.70