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	$178.86	9.255%	$195.4135	$195.41	$195.40	$195.40
Purchase #2	$98.66	5.630%	$104.2146	$104.21	$104.20	$104.20
Purchase #3	$85.59	5.331%	$90.1528	$90.15	$90.15	$90.20
Purchase #4	$98.71	5.785%	$104.4204	$104.42	$104.40	$104.40
Purchase #5	$44.78	4.648%	$46.8614	$46.86	$46.85	$46.90
Purchase #6	$90.95	10.339%	$100.3533	$100.35	$100.35	$100.40
Purchase #7	$240.68	8.839%	$261.9537	$261.95	$261.95	$262.00
7 purchase totals =	$838.23		$903.3697	$903.35	$903.30	$903.50