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	$227.71	3.726%	$236.1945	$236.19	$236.20	$236.20
Purchase #2	$183.44	5.764%	$194.0135	$194.01	$194.00	$194.00
Purchase #3	$214.91	9.262%	$234.815	$234.82	$234.80	$234.80
Purchase #4	$93.92	10.583%	$103.8596	$103.86	$103.85	$103.90
Purchase #5	$13.60	4.768%	$14.2484	$14.25	$14.25	$14.20
Purchase #6	$34.45	8.739%	$37.4606	$37.46	$37.45	$37.50
Purchase #7	$182.82	7.260%	$196.0927	$196.09	$196.10	$196.10
7 purchase totals =	$950.85		$1,016.6843	$1,016.68	$1,016.65	$1,016.70