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	$106.42	8.440%	$115.4018	$115.40	$115.40	$115.40
Purchase #2	$211.72	12.768%	$238.7524	$238.75	$238.75	$238.80
Purchase #3	$243.27	6.244%	$258.4598	$258.46	$258.45	$258.50
Purchase #4	$13.94	3.443%	$14.42	$14.42	$14.40	$14.40
Purchase #5	$179.83	9.227%	$196.4229	$196.42	$196.40	$196.40
Purchase #6	$99.40	5.274%	$104.6424	$104.64	$104.65	$104.60
Purchase #7	$231.57	8.587%	$251.4549	$251.45	$251.45	$251.50
7 purchase totals =	$1,086.15		$1,179.5542	$1,179.54	$1,179.50	$1,179.60