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	$12.98	11.718%	$14.501	$14.50	$14.50	$14.50
Purchase #2	$85.50	6.176%	$90.7805	$90.78	$90.80	$90.80
Purchase #3	$197.59	7.293%	$212.0002	$212.00	$212.00	$212.00
Purchase #4	$87.85	5.660%	$92.8223	$92.82	$92.80	$92.80
Purchase #5	$201.52	4.664%	$210.9189	$210.92	$210.90	$210.90
Purchase #6	$118.79	11.350%	$132.2727	$132.27	$132.25	$132.30
Purchase #7	$153.60	4.110%	$159.913	$159.91	$159.90	$159.90
7 purchase totals =	$857.83		$913.2086	$913.20	$913.15	$913.20