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	$62.69	8.322%	$67.9071	$67.91	$67.90	$67.90
Purchase #2	$57.97	5.304%	$61.0447	$61.04	$61.05	$61.00
Purchase #3	$215.44	9.604%	$236.1309	$236.13	$236.15	$236.10
Purchase #4	$146.32	6.557%	$155.9142	$155.91	$155.90	$155.90
Purchase #5	$225.81	13.351%	$255.9579	$255.96	$255.95	$256.00
Purchase #6	$7.66	12.576%	$8.6233	$8.62	$8.60	$8.60
Purchase #7	$203.58	13.376%	$230.8109	$230.81	$230.80	$230.80
7 purchase totals =	$919.47		$1,016.3890	$1,016.38	$1,016.35	$1,016.30