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	$176.89	12.431%	$198.8792	$198.88	$198.90	$198.90
Purchase #2	$218.27	6.211%	$231.8267	$231.83	$231.85	$231.80
Purchase #3	$30.94	7.853%	$33.3697	$33.37	$33.35	$33.40
Purchase #4	$237.45	7.719%	$255.7788	$255.78	$255.80	$255.80
Purchase #5	$95.49	10.403%	$105.4238	$105.42	$105.40	$105.40
Purchase #6	$73.63	12.652%	$82.9457	$82.95	$82.95	$82.90
Purchase #7	$226.45	4.334%	$236.2643	$236.26	$236.25	$236.30
7 purchase totals =	$1,059.12		$1,144.4882	$1,144.49	$1,144.50	$1,144.50