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	$222.47	5.375%	$234.4278	$234.43	$234.45	$234.40
Purchase #2	$43.35	11.529%	$48.3478	$48.35	$48.35	$48.30
Purchase #3	$136.80	4.863%	$143.4526	$143.45	$143.45	$143.50
Purchase #4	$80.58	7.324%	$86.4817	$86.48	$86.50	$86.50
Purchase #5	$52.58	10.146%	$57.9148	$57.91	$57.90	$57.90
Purchase #6	$72.83	6.313%	$77.4278	$77.43	$77.45	$77.40
Purchase #7	$124.49	9.785%	$136.6713	$136.67	$136.65	$136.70
7 purchase totals =	$733.10		$784.7238	$784.72	$784.75	$784.70