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	$218.31	9.529%	$239.1128	$239.11	$239.10	$239.10
Purchase #2	$43.55	7.665%	$46.8881	$46.89	$46.90	$46.90
Purchase #3	$111.54	13.696%	$126.8165	$126.82	$126.80	$126.80
Purchase #4	$227.42	5.429%	$239.7666	$239.77	$239.75	$239.80
Purchase #5	$109.29	13.339%	$123.8682	$123.87	$123.85	$123.90
Purchase #6	$71.36	12.528%	$80.3	$80.30	$80.30	$80.30
Purchase #7	$223.29	3.320%	$230.7032	$230.70	$230.70	$230.70
7 purchase totals =	$1,004.76		$1,087.4554	$1,087.46	$1,087.40	$1,087.50