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	$148.70	4.275%	$155.0569	$155.06	$155.05	$155.10
Purchase #2	$106.71	5.762%	$112.8586	$112.86	$112.85	$112.90
Purchase #3	$152.94	6.205%	$162.4299	$162.43	$162.45	$162.40
Purchase #4	$97.53	4.464%	$101.8837	$101.88	$101.90	$101.90
Purchase #5	$238.67	8.694%	$259.42	$259.42	$259.40	$259.40
Purchase #6	$146.66	10.815%	$162.5213	$162.52	$162.50	$162.50
Purchase #7	$46.60	9.578%	$51.0633	$51.06	$51.05	$51.10
7 purchase totals =	$937.81		$1,005.2337	$1,005.23	$1,005.20	$1,005.30