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	$40.53	6.645%	$43.2232	$43.22	$43.20	$43.20
Purchase #2	$71.38	7.244%	$76.5508	$76.55	$76.55	$76.60
Purchase #3	$160.31	13.438%	$181.8525	$181.85	$181.85	$181.90
Purchase #4	$212.60	12.341%	$238.837	$238.84	$238.85	$238.80
Purchase #5	$101.69	3.791%	$105.5451	$105.55	$105.55	$105.50
Purchase #6	$10.46	7.104%	$11.2031	$11.20	$11.20	$11.20
Purchase #7	$65.71	10.167%	$72.3907	$72.39	$72.40	$72.40
7 purchase totals =	$662.68		$729.6024	$729.60	$729.60	$729.60