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	$178.77	8.813%	$194.525	$194.53	$194.55	$194.50
Purchase #2	$111.92	4.871%	$117.3716	$117.37	$117.35	$117.40
Purchase #3	$213.72	10.387%	$235.9191	$235.92	$235.90	$235.90
Purchase #4	$132.76	13.670%	$150.9083	$150.91	$150.90	$150.90
Purchase #5	$81.38	9.415%	$89.0419	$89.04	$89.05	$89.00
Purchase #6	$248.86	10.339%	$274.5896	$274.59	$274.60	$274.60
Purchase #7	$232.82	10.313%	$256.8307	$256.83	$256.85	$256.80
7 purchase totals =	$1,200.23		$1,319.1862	$1,319.19	$1,319.20	$1,319.10