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	$227.73	9.555%	$249.4896	$249.49	$249.50	$249.50
Purchase #2	$192.59	4.198%	$200.6749	$200.67	$200.65	$200.70
Purchase #3	$74.33	9.806%	$81.6188	$81.62	$81.60	$81.60
Purchase #4	$38.50	6.462%	$40.9879	$40.99	$41.00	$41.00
Purchase #5	$42.32	11.471%	$47.1745	$47.17	$47.15	$47.20
Purchase #6	$204.63	5.482%	$215.8478	$215.85	$215.85	$215.80
Purchase #7	$103.72	5.594%	$109.5221	$109.52	$109.50	$109.50
7 purchase totals =	$883.82		$945.3156	$945.31	$945.25	$945.30