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	$41.88	11.162%	$46.5546	$46.55	$46.55	$46.60
Purchase #2	$71.29	3.540%	$73.8137	$73.81	$73.80	$73.80
Purchase #3	$124.25	8.600%	$134.9355	$134.94	$134.95	$134.90
Purchase #4	$63.85	4.757%	$66.8873	$66.89	$66.90	$66.90
Purchase #5	$87.54	7.240%	$93.8779	$93.88	$93.90	$93.90
Purchase #6	$93.52	11.521%	$104.2944	$104.29	$104.30	$104.30
Purchase #7	$57.43	3.159%	$59.2442	$59.24	$59.25	$59.20
7 purchase totals =	$539.76		$579.6076	$579.60	$579.65	$579.60