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	$107.45	9.458%	$117.6126	$117.61	$117.60	$117.60
Purchase #2	$41.94	10.793%	$46.4666	$46.47	$46.45	$46.50
Purchase #3	$134.91	12.869%	$152.2716	$152.27	$152.25	$152.30
Purchase #4	$128.57	12.392%	$144.5024	$144.50	$144.50	$144.50
Purchase #5	$197.34	5.662%	$208.5134	$208.51	$208.50	$208.50
Purchase #6	$139.71	4.643%	$146.1967	$146.20	$146.20	$146.20
Purchase #7	$182.53	7.323%	$195.8967	$195.90	$195.90	$195.90
7 purchase totals =	$932.45		$1,011.4600	$1,011.46	$1,011.40	$1,011.50