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	$68.44	13.156%	$77.444	$77.44	$77.45	$77.40
Purchase #2	$66.26	9.273%	$72.4043	$72.40	$72.40	$72.40
Purchase #3	$178.89	11.315%	$199.1314	$199.13	$199.15	$199.10
Purchase #4	$236.41	3.634%	$245.0011	$245.00	$245.00	$245.00
Purchase #5	$35.87	4.418%	$37.4547	$37.45	$37.45	$37.50
Purchase #6	$225.65	10.845%	$250.1217	$250.12	$250.10	$250.10
Purchase #7	$19.71	10.653%	$21.8097	$21.81	$21.80	$21.80
7 purchase totals =	$831.23		$903.3669	$903.35	$903.35	$903.30