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	$117.78	4.781%	$123.4111	$123.41	$123.40	$123.40
Purchase #2	$235.27	9.221%	$256.9642	$256.96	$256.95	$257.00
Purchase #3	$103.72	3.576%	$107.429	$107.43	$107.45	$107.40
Purchase #4	$6.45	4.656%	$6.7503	$6.75	$6.75	$6.80
Purchase #5	$104.93	4.373%	$109.5186	$109.52	$109.50	$109.50
Purchase #6	$52.95	13.220%	$59.95	$59.95	$59.95	$60.00
Purchase #7	$189.94	5.369%	$200.1379	$200.14	$200.15	$200.10
7 purchase totals =	$811.04		$864.1611	$864.16	$864.15	$864.20