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	$82.92	11.755%	$92.6672	$92.67	$92.65	$92.70
Purchase #2	$18.25	3.262%	$18.8453	$18.85	$18.85	$18.80
Purchase #3	$90.90	9.476%	$99.5137	$99.51	$99.50	$99.50
Purchase #4	$63.94	4.340%	$66.715	$66.72	$66.70	$66.70
Purchase #5	$218.59	6.748%	$233.3405	$233.34	$233.35	$233.30
Purchase #6	$204.80	7.746%	$220.6638	$220.66	$220.65	$220.70
Purchase #7	$90.64	12.273%	$101.7642	$101.76	$101.75	$101.80
7 purchase totals =	$770.04		$833.5097	$833.51	$833.45	$833.50