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	$91.45	10.275%	$100.8465	$100.85	$100.85	$100.80
Purchase #2	$86.75	8.448%	$94.0786	$94.08	$94.10	$94.10
Purchase #3	$199.75	12.805%	$225.328	$225.33	$225.35	$225.30
Purchase #4	$225.30	4.233%	$234.8369	$234.84	$234.85	$234.80
Purchase #5	$19.75	9.335%	$21.5937	$21.59	$21.60	$21.60
Purchase #6	$42.87	13.410%	$48.6189	$48.62	$48.60	$48.60
Purchase #7	$215.92	3.154%	$222.7301	$222.73	$222.75	$222.70
7 purchase totals =	$881.79		$948.0327	$948.04	$948.10	$947.90