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	$17.79	8.293%	$19.2653	$19.27	$19.25	$19.30
Purchase #2	$63.41	12.705%	$71.4662	$71.47	$71.45	$71.50
Purchase #3	$105.72	7.475%	$113.6226	$113.62	$113.60	$113.60
Purchase #4	$208.86	8.466%	$226.5421	$226.54	$226.55	$226.50
Purchase #5	$103.60	10.761%	$114.7484	$114.75	$114.75	$114.70
Purchase #6	$232.48	12.812%	$262.2653	$262.27	$262.25	$262.30
Purchase #7	$248.59	9.611%	$272.482	$272.48	$272.50	$272.50
7 purchase totals =	$980.45		$1,080.3919	$1,080.40	$1,080.35	$1,080.40