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	$140.69	12.746%	$158.6223	$158.62	$158.60	$158.60
Purchase #2	$40.70	7.617%	$43.8001	$43.80	$43.80	$43.80
Purchase #3	$108.75	3.309%	$112.3485	$112.35	$112.35	$112.30
Purchase #4	$81.91	9.235%	$89.4744	$89.47	$89.45	$89.50
Purchase #5	$191.33	3.561%	$198.1433	$198.14	$198.15	$198.10
Purchase #6	$172.34	7.537%	$185.3293	$185.33	$185.35	$185.30
Purchase #7	$149.65	5.215%	$157.4542	$157.45	$157.45	$157.50
7 purchase totals =	$885.37		$945.1721	$945.16	$945.15	$945.10