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	$141.37	10.238%	$155.8435	$155.84	$155.85	$155.80
Purchase #2	$16.84	12.601%	$18.962	$18.96	$18.95	$19.00
Purchase #3	$131.47	10.408%	$145.1534	$145.15	$145.15	$145.20
Purchase #4	$146.58	8.184%	$158.5761	$158.58	$158.60	$158.60
Purchase #5	$249.85	6.215%	$265.3782	$265.38	$265.40	$265.40
Purchase #6	$241.64	7.533%	$259.8427	$259.84	$259.85	$259.80
Purchase #7	$97.95	7.587%	$105.3815	$105.38	$105.40	$105.40
7 purchase totals =	$1,025.70		$1,109.1374	$1,109.13	$1,109.20	$1,109.20