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	$112.75	9.720%	$123.7093	$123.71	$123.70	$123.70
Purchase #2	$62.25	13.822%	$70.8542	$70.85	$70.85	$70.90
Purchase #3	$112.91	4.154%	$117.6003	$117.60	$117.60	$117.60
Purchase #4	$79.35	3.441%	$82.0804	$82.08	$82.10	$82.10
Purchase #5	$21.59	10.591%	$23.8766	$23.88	$23.90	$23.90
Purchase #6	$141.50	11.442%	$157.6904	$157.69	$157.70	$157.70
Purchase #7	$176.37	13.828%	$200.7584	$200.76	$200.75	$200.80
7 purchase totals =	$706.72		$776.5696	$776.57	$776.60	$776.70