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	$199.46	7.184%	$213.7892	$213.79	$213.80	$213.80
Purchase #2	$59.37	8.380%	$64.3452	$64.35	$64.35	$64.30
Purchase #3	$40.57	5.631%	$42.8545	$42.85	$42.85	$42.90
Purchase #4	$163.87	6.382%	$174.3282	$174.33	$174.35	$174.30
Purchase #5	$81.48	8.830%	$88.6747	$88.67	$88.65	$88.70
Purchase #6	$111.38	10.849%	$123.4636	$123.46	$123.45	$123.50
Purchase #7	$6.53	4.484%	$6.8228	$6.82	$6.80	$6.80
7 purchase totals =	$662.66		$714.2782	$714.27	$714.25	$714.30