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	$210.33	13.405%	$238.5247	$238.52	$238.50	$238.50
Purchase #2	$84.64	13.338%	$95.9293	$95.93	$95.95	$95.90
Purchase #3	$59.72	3.636%	$61.8914	$61.89	$61.90	$61.90
Purchase #4	$96.38	11.166%	$107.1418	$107.14	$107.15	$107.10
Purchase #5	$126.35	4.783%	$132.3933	$132.39	$132.40	$132.40
Purchase #6	$181.71	6.660%	$193.8119	$193.81	$193.80	$193.80
Purchase #7	$233.46	9.271%	$255.1041	$255.10	$255.10	$255.10
7 purchase totals =	$992.59		$1,084.7965	$1,084.78	$1,084.80	$1,084.70