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	$214.59	6.367%	$228.2529	$228.25	$228.25	$228.30
Purchase #2	$156.68	5.189%	$164.8101	$164.81	$164.80	$164.80
Purchase #3	$58.34	8.237%	$63.1455	$63.15	$63.15	$63.10
Purchase #4	$171.30	3.256%	$176.8775	$176.88	$176.90	$176.90
Purchase #5	$124.93	5.343%	$131.605	$131.61	$131.60	$131.60
Purchase #6	$203.33	6.640%	$216.8311	$216.83	$216.85	$216.80
Purchase #7	$169.34	8.613%	$183.9253	$183.93	$183.95	$183.90
7 purchase totals =	$1,098.51		$1,165.4474	$1,165.46	$1,165.50	$1,165.40