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	$245.64	8.725%	$267.0721	$267.07	$267.05	$267.10
Purchase #2	$17.71	13.587%	$20.1163	$20.12	$20.10	$20.10
Purchase #3	$96.70	3.466%	$100.0516	$100.05	$100.05	$100.10
Purchase #4	$132.56	6.268%	$140.8689	$140.87	$140.85	$140.90
Purchase #5	$103.29	10.795%	$114.4402	$114.44	$114.45	$114.40
Purchase #6	$93.99	6.644%	$100.2347	$100.23	$100.25	$100.20
Purchase #7	$108.42	4.798%	$113.622	$113.62	$113.60	$113.60
7 purchase totals =	$798.31		$856.4058	$856.40	$856.35	$856.40