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	$8.28	6.802%	$8.8432	$8.84	$8.85	$8.80
Purchase #2	$154.37	9.337%	$168.7835	$168.78	$168.80	$168.80
Purchase #3	$111.37	3.632%	$115.415	$115.42	$115.40	$115.40
Purchase #4	$95.36	8.529%	$103.4933	$103.49	$103.50	$103.50
Purchase #5	$69.25	4.149%	$72.1232	$72.12	$72.10	$72.10
Purchase #6	$142.92	5.401%	$150.6391	$150.64	$150.65	$150.60
Purchase #7	$207.37	3.752%	$215.1505	$215.15	$215.15	$215.20
7 purchase totals =	$788.92		$834.4478	$834.44	$834.45	$834.40