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	$53.29	4.208%	$55.5324	$55.53	$55.55	$55.50
Purchase #2	$117.64	11.235%	$130.8569	$130.86	$130.85	$130.90
Purchase #3	$136.52	10.151%	$150.3781	$150.38	$150.40	$150.40
Purchase #4	$202.65	12.149%	$227.2699	$227.27	$227.25	$227.30
Purchase #5	$171.98	12.301%	$193.1353	$193.14	$193.15	$193.10
Purchase #6	$20.33	7.175%	$21.7887	$21.79	$21.80	$21.80
Purchase #7	$73.31	11.311%	$81.6021	$81.60	$81.60	$81.60
7 purchase totals =	$775.72		$860.5634	$860.57	$860.60	$860.60