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	$146.89	10.610%	$162.475	$162.48	$162.50	$162.50
Purchase #2	$62.43	13.489%	$70.8512	$70.85	$70.85	$70.90
Purchase #3	$158.63	4.177%	$165.256	$165.26	$165.25	$165.30
Purchase #4	$176.96	5.395%	$186.507	$186.51	$186.50	$186.50
Purchase #5	$189.50	5.267%	$199.481	$199.48	$199.50	$199.50
Purchase #6	$189.46	12.737%	$213.5915	$213.59	$213.60	$213.60
Purchase #7	$90.84	8.509%	$98.5696	$98.57	$98.55	$98.60
7 purchase totals =	$1,014.71		$1,096.7313	$1,096.74	$1,096.75	$1,096.90