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	$156.59	4.288%	$163.3046	$163.30	$163.30	$163.30
Purchase #2	$10.55	11.729%	$11.7874	$11.79	$11.80	$11.80
Purchase #3	$15.48	3.407%	$16.0074	$16.01	$16.00	$16.00
Purchase #4	$98.67	5.727%	$104.3208	$104.32	$104.30	$104.30
Purchase #5	$108.72	13.679%	$123.5918	$123.59	$123.60	$123.60
Purchase #6	$97.77	8.211%	$105.7979	$105.80	$105.80	$105.80
Purchase #7	$141.61	10.523%	$156.5116	$156.51	$156.50	$156.50
7 purchase totals =	$629.39		$681.3215	$681.32	$681.30	$681.30