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	$218.72	8.150%	$236.5457	$236.55	$236.55	$236.50
Purchase #2	$43.57	10.121%	$47.9797	$47.98	$48.00	$48.00
Purchase #3	$103.68	7.399%	$111.3513	$111.35	$111.35	$111.40
Purchase #4	$119.31	3.105%	$123.0146	$123.01	$123.00	$123.00
Purchase #5	$56.87	5.757%	$60.144	$60.14	$60.15	$60.10
Purchase #6	$105.60	7.671%	$113.7006	$113.70	$113.70	$113.70
Purchase #7	$65.80	10.782%	$72.8946	$72.89	$72.90	$72.90
7 purchase totals =	$713.55		$765.6305	$765.62	$765.65	$765.60