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	$38.67	12.625%	$43.5521	$43.55	$43.55	$43.60
Purchase #2	$200.63	13.159%	$227.0309	$227.03	$227.05	$227.00
Purchase #3	$119.51	3.434%	$123.614	$123.61	$123.60	$123.60
Purchase #4	$54.32	9.590%	$59.5293	$59.53	$59.55	$59.50
Purchase #5	$111.40	4.579%	$116.501	$116.50	$116.50	$116.50
Purchase #6	$127.38	9.633%	$139.6505	$139.65	$139.65	$139.70
Purchase #7	$86.45	4.722%	$90.5322	$90.53	$90.55	$90.50
7 purchase totals =	$738.36		$800.4100	$800.40	$800.45	$800.40