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	$224.59	6.359%	$238.8717	$238.87	$238.85	$238.90
Purchase #2	$45.31	6.572%	$48.2878	$48.29	$48.30	$48.30
Purchase #3	$199.60	11.686%	$222.9253	$222.93	$222.95	$222.90
Purchase #4	$139.50	10.712%	$154.4432	$154.44	$154.45	$154.40
Purchase #5	$165.52	5.171%	$174.079	$174.08	$174.10	$174.10
Purchase #6	$81.59	10.772%	$90.3789	$90.38	$90.40	$90.40
Purchase #7	$244.75	13.351%	$277.4266	$277.43	$277.45	$277.40
7 purchase totals =	$1,100.86		$1,206.4125	$1,206.42	$1,206.50	$1,206.40