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	$66.93	5.661%	$70.7189	$70.72	$70.70	$70.70
Purchase #2	$207.60	4.782%	$217.5274	$217.53	$217.55	$217.50
Purchase #3	$98.27	6.153%	$104.3166	$104.32	$104.30	$104.30
Purchase #4	$200.43	13.326%	$227.1393	$227.14	$227.15	$227.10
Purchase #5	$119.37	3.534%	$123.5885	$123.59	$123.60	$123.60
Purchase #6	$150.35	7.587%	$161.7571	$161.76	$161.75	$161.80
Purchase #7	$104.57	9.344%	$114.341	$114.34	$114.35	$114.30
7 purchase totals =	$947.52		$1,019.3888	$1,019.40	$1,019.40	$1,019.30