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	$100.88	11.104%	$112.0817	$112.08	$112.10	$112.10
Purchase #2	$71.46	13.509%	$81.1135	$81.11	$81.10	$81.10
Purchase #3	$66.39	7.870%	$71.6149	$71.61	$71.60	$71.60
Purchase #4	$81.72	10.252%	$90.0979	$90.10	$90.10	$90.10
Purchase #5	$138.25	4.513%	$144.4892	$144.49	$144.50	$144.50
Purchase #6	$34.35	5.542%	$36.2537	$36.25	$36.25	$36.30
Purchase #7	$79.75	12.347%	$89.5967	$89.60	$89.60	$89.60
7 purchase totals =	$572.80		$625.2476	$625.24	$625.25	$625.30