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	$180.84	8.678%	$196.5333	$196.53	$196.55	$196.50
Purchase #2	$113.40	3.373%	$117.225	$117.23	$117.25	$117.20
Purchase #3	$98.83	7.682%	$106.4221	$106.42	$106.40	$106.40
Purchase #4	$83.92	13.724%	$95.4372	$95.44	$95.45	$95.40
Purchase #5	$97.52	5.195%	$102.5862	$102.59	$102.60	$102.60
Purchase #6	$18.58	13.555%	$21.0985	$21.10	$21.10	$21.10
Purchase #7	$160.26	3.620%	$166.0614	$166.06	$166.05	$166.10
7 purchase totals =	$753.35		$805.3637	$805.37	$805.40	$805.30