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	$42.89	6.491%	$45.674	$45.67	$45.65	$45.70
Purchase #2	$43.32	10.758%	$47.9804	$47.98	$48.00	$48.00
Purchase #3	$101.50	3.308%	$104.8576	$104.86	$104.85	$104.90
Purchase #4	$111.87	4.848%	$117.2935	$117.29	$117.30	$117.30
Purchase #5	$208.31	10.651%	$230.4971	$230.50	$230.50	$230.50
Purchase #6	$57.80	13.691%	$65.7134	$65.71	$65.70	$65.70
Purchase #7	$167.75	8.846%	$182.5892	$182.59	$182.60	$182.60
7 purchase totals =	$733.44		$794.6052	$794.60	$794.60	$794.70