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	$18.41	8.388%	$19.9542	$19.95	$19.95	$20.00
Purchase #2	$39.82	10.134%	$43.8554	$43.86	$43.85	$43.90
Purchase #3	$69.94	12.105%	$78.4062	$78.41	$78.40	$78.40
Purchase #4	$118.90	8.160%	$128.6022	$128.60	$128.60	$128.60
Purchase #5	$139.56	4.772%	$146.2198	$146.22	$146.20	$146.20
Purchase #6	$143.94	4.397%	$150.269	$150.27	$150.25	$150.30
Purchase #7	$135.60	6.630%	$144.5903	$144.59	$144.60	$144.60
7 purchase totals =	$666.17		$711.8971	$711.90	$711.85	$712.00