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	$43.98	3.610%	$45.5677	$45.57	$45.55	$45.60
Purchase #2	$200.47	13.264%	$227.0603	$227.06	$227.05	$227.10
Purchase #3	$63.49	6.365%	$67.5311	$67.53	$67.55	$67.50
Purchase #4	$183.34	13.530%	$208.1459	$208.15	$208.15	$208.10
Purchase #5	$38.63	5.344%	$40.6944	$40.69	$40.70	$40.70
Purchase #6	$164.93	6.222%	$175.1919	$175.19	$175.20	$175.20
Purchase #7	$202.97	5.720%	$214.5799	$214.58	$214.60	$214.60
7 purchase totals =	$897.81		$978.7712	$978.77	$978.80	$978.80