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	$87.43	9.138%	$95.4194	$95.42	$95.40	$95.40
Purchase #2	$49.64	9.111%	$54.1627	$54.16	$54.15	$54.20
Purchase #3	$127.26	4.363%	$132.8124	$132.81	$132.80	$132.80
Purchase #4	$183.55	6.534%	$195.5432	$195.54	$195.55	$195.50
Purchase #5	$121.25	8.715%	$131.8169	$131.82	$131.80	$131.80
Purchase #6	$155.35	4.588%	$162.4775	$162.48	$162.50	$162.50
Purchase #7	$82.48	9.125%	$90.0063	$90.01	$90.00	$90.00
7 purchase totals =	$806.96		$862.2384	$862.24	$862.20	$862.20