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	$14.97	3.598%	$15.5086	$15.51	$15.50	$15.50
Purchase #2	$51.31	3.619%	$53.1669	$53.17	$53.15	$53.20
Purchase #3	$200.64	12.330%	$225.3789	$225.38	$225.40	$225.40
Purchase #4	$87.65	9.325%	$95.8234	$95.82	$95.80	$95.80
Purchase #5	$43.77	9.447%	$47.905	$47.91	$47.90	$47.90
Purchase #6	$40.86	13.492%	$46.3728	$46.37	$46.35	$46.40
Purchase #7	$68.50	13.587%	$77.8071	$77.81	$77.80	$77.80
7 purchase totals =	$507.70		$561.9627	$561.97	$561.90	$562.00