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	$135.81	9.588%	$148.8315	$148.83	$148.85	$148.80
Purchase #2	$140.54	8.499%	$152.4845	$152.48	$152.50	$152.50
Purchase #3	$206.49	11.654%	$230.5543	$230.55	$230.55	$230.60
Purchase #4	$186.80	3.387%	$193.1269	$193.13	$193.15	$193.10
Purchase #5	$40.27	5.863%	$42.631	$42.63	$42.65	$42.60
Purchase #6	$123.93	7.687%	$133.4565	$133.46	$133.45	$133.50
Purchase #7	$114.90	10.538%	$127.0082	$127.01	$127.00	$127.00
7 purchase totals =	$948.74		$1,028.0929	$1,028.09	$1,028.15	$1,028.10