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	$215.42	8.526%	$233.7867	$233.79	$233.80	$233.80
Purchase #2	$158.28	4.720%	$165.7508	$165.75	$165.75	$165.80
Purchase #3	$148.69	6.743%	$158.7162	$158.72	$158.70	$158.70
Purchase #4	$164.71	10.553%	$182.0918	$182.09	$182.10	$182.10
Purchase #5	$191.63	7.193%	$205.4139	$205.41	$205.40	$205.40
Purchase #6	$43.77	12.177%	$49.0999	$49.10	$49.10	$49.10
Purchase #7	$18.85	13.198%	$21.3378	$21.34	$21.35	$21.30
7 purchase totals =	$941.35		$1,016.1971	$1,016.20	$1,016.20	$1,016.20