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	$110.33	6.836%	$117.8722	$117.87	$117.85	$117.90
Purchase #2	$24.47	4.705%	$25.6213	$25.62	$25.60	$25.60
Purchase #3	$131.39	4.271%	$137.0017	$137.00	$137.00	$137.00
Purchase #4	$38.94	7.732%	$41.9508	$41.95	$41.95	$42.00
Purchase #5	$241.82	11.553%	$269.7575	$269.76	$269.75	$269.80
Purchase #6	$112.79	9.764%	$123.8028	$123.80	$123.80	$123.80
Purchase #7	$161.37	3.774%	$167.4601	$167.46	$167.45	$167.50
7 purchase totals =	$821.11		$883.4664	$883.46	$883.40	$883.60