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	$122.93	3.693%	$127.4698	$127.47	$127.45	$127.50
Purchase #2	$246.52	5.565%	$260.2388	$260.24	$260.25	$260.20
Purchase #3	$249.52	5.655%	$263.6304	$263.63	$263.65	$263.60
Purchase #4	$126.82	4.591%	$132.6423	$132.64	$132.65	$132.60
Purchase #5	$210.85	11.300%	$234.6761	$234.68	$234.70	$234.70
Purchase #6	$73.91	5.569%	$78.026	$78.03	$78.05	$78.00
Purchase #7	$138.27	11.255%	$153.8323	$153.83	$153.85	$153.80
7 purchase totals =	$1,168.82		$1,250.5157	$1,250.52	$1,250.60	$1,250.40