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	$192.66	13.605%	$218.8714	$218.87	$218.85	$218.90
Purchase #2	$104.47	11.361%	$116.3388	$116.34	$116.35	$116.30
Purchase #3	$28.58	10.226%	$31.5026	$31.50	$31.50	$31.50
Purchase #4	$159.38	9.553%	$174.6056	$174.61	$174.60	$174.60
Purchase #5	$184.39	11.363%	$205.3422	$205.34	$205.35	$205.30
Purchase #6	$17.71	13.319%	$20.0688	$20.07	$20.05	$20.10
Purchase #7	$191.73	4.716%	$200.772	$200.77	$200.75	$200.80
7 purchase totals =	$878.92		$967.5014	$967.50	$967.45	$967.50