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	$102.27	3.536%	$105.8863	$105.89	$105.90	$105.90
Purchase #2	$62.29	13.321%	$70.5877	$70.59	$70.60	$70.60
Purchase #3	$194.78	7.109%	$208.6269	$208.63	$208.65	$208.60
Purchase #4	$212.37	6.366%	$225.8895	$225.89	$225.90	$225.90
Purchase #5	$148.48	9.670%	$162.838	$162.84	$162.85	$162.80
Purchase #6	$131.59	8.768%	$143.1278	$143.13	$143.15	$143.10
Purchase #7	$83.75	9.164%	$91.4249	$91.42	$91.40	$91.40
7 purchase totals =	$935.53		$1,008.3811	$1,008.39	$1,008.45	$1,008.30