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	$48.68	10.761%	$53.9185	$53.92	$53.90	$53.90
Purchase #2	$106.53	9.153%	$116.2807	$116.28	$116.30	$116.30
Purchase #3	$56.89	8.221%	$61.5669	$61.57	$61.55	$61.60
Purchase #4	$124.92	4.408%	$130.4265	$130.43	$130.45	$130.40
Purchase #5	$116.51	6.244%	$123.7849	$123.78	$123.80	$123.80
Purchase #6	$25.77	6.619%	$27.4757	$27.48	$27.50	$27.50
Purchase #7	$146.38	11.446%	$163.1347	$163.13	$163.15	$163.10
7 purchase totals =	$625.68		$676.5879	$676.59	$676.65	$676.60