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	$125.70	12.156%	$140.9801	$140.98	$141.00	$141.00
Purchase #2	$9.41	4.597%	$9.8426	$9.84	$9.85	$9.80
Purchase #3	$95.33	4.747%	$99.8553	$99.86	$99.85	$99.90
Purchase #4	$51.52	6.584%	$54.9121	$54.91	$54.90	$54.90
Purchase #5	$248.65	12.806%	$280.4921	$280.49	$280.50	$280.50
Purchase #6	$109.55	13.153%	$123.9591	$123.96	$123.95	$124.00
Purchase #7	$11.37	4.557%	$11.8881	$11.89	$11.90	$11.90
7 purchase totals =	$651.53		$721.9294	$721.93	$721.95	$722.00