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	$173.77	4.278%	$181.2039	$181.20	$181.20	$181.20
Purchase #2	$201.89	10.183%	$222.4485	$222.45	$222.45	$222.40
Purchase #3	$239.78	7.105%	$256.8164	$256.82	$256.80	$256.80
Purchase #4	$125.81	9.252%	$137.4499	$137.45	$137.45	$137.40
Purchase #5	$17.35	11.633%	$19.3683	$19.37	$19.35	$19.40
Purchase #6	$104.76	3.539%	$108.4675	$108.47	$108.45	$108.50
Purchase #7	$215.25	9.770%	$236.2799	$236.28	$236.30	$236.30
7 purchase totals =	$1,078.61		$1,162.0344	$1,162.04	$1,162.00	$1,162.00