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	$148.47	13.455%	$168.4466	$168.45	$168.45	$168.40
Purchase #2	$123.69	4.245%	$128.9406	$128.94	$128.95	$128.90
Purchase #3	$64.28	13.509%	$72.9636	$72.96	$72.95	$73.00
Purchase #4	$137.93	12.120%	$154.6471	$154.65	$154.65	$154.60
Purchase #5	$91.82	9.680%	$100.7082	$100.71	$100.70	$100.70
Purchase #6	$217.41	4.673%	$227.5696	$227.57	$227.55	$227.60
Purchase #7	$168.52	13.784%	$191.7488	$191.75	$191.75	$191.70
7 purchase totals =	$952.12		$1,045.0245	$1,045.03	$1,045.00	$1,044.90