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	$59.57	13.630%	$67.6894	$67.69	$67.70	$67.70
Purchase #2	$34.32	3.456%	$35.5061	$35.51	$35.50	$35.50
Purchase #3	$213.73	9.450%	$233.9275	$233.93	$233.95	$233.90
Purchase #4	$94.46	11.827%	$105.6318	$105.63	$105.65	$105.60
Purchase #5	$12.62	10.743%	$13.9758	$13.98	$14.00	$14.00
Purchase #6	$210.85	13.576%	$239.475	$239.48	$239.50	$239.50
Purchase #7	$76.50	7.849%	$82.5045	$82.50	$82.50	$82.50
7 purchase totals =	$702.05		$778.7101	$778.72	$778.80	$778.70