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	$234.29	7.162%	$251.0698	$251.07	$251.05	$251.10
Purchase #2	$85.65	8.239%	$92.7067	$92.71	$92.70	$92.70
Purchase #3	$137.36	3.713%	$142.4602	$142.46	$142.45	$142.50
Purchase #4	$181.28	3.401%	$187.4453	$187.45	$187.45	$187.40
Purchase #5	$220.68	9.383%	$241.3864	$241.39	$241.40	$241.40
Purchase #6	$109.72	4.509%	$114.6673	$114.67	$114.65	$114.70
Purchase #7	$63.94	10.857%	$70.882	$70.88	$70.90	$70.90
7 purchase totals =	$1,032.92		$1,100.6177	$1,100.63	$1,100.60	$1,100.70