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	$105.36	11.274%	$117.2383	$117.24	$117.25	$117.20
Purchase #2	$9.31	13.780%	$10.5929	$10.59	$10.60	$10.60
Purchase #3	$116.40	3.553%	$120.5357	$120.54	$120.55	$120.50
Purchase #4	$108.55	13.382%	$123.0762	$123.08	$123.10	$123.10
Purchase #5	$233.83	4.780%	$245.0071	$245.01	$245.00	$245.00
Purchase #6	$146.57	13.749%	$166.7219	$166.72	$166.70	$166.70
Purchase #7	$170.58	8.844%	$185.6661	$185.67	$185.65	$185.70
7 purchase totals =	$890.60		$968.8382	$968.85	$968.85	$968.80