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	$138.59	9.691%	$152.0208	$152.02	$152.00	$152.00
Purchase #2	$77.87	9.347%	$85.1485	$85.15	$85.15	$85.10
Purchase #3	$198.25	12.223%	$222.4821	$222.48	$222.50	$222.50
Purchase #4	$43.44	9.330%	$47.493	$47.49	$47.50	$47.50
Purchase #5	$212.96	10.130%	$234.5328	$234.53	$234.55	$234.50
Purchase #6	$63.42	3.693%	$65.7621	$65.76	$65.75	$65.80
Purchase #7	$70.52	7.857%	$76.0608	$76.06	$76.05	$76.10
7 purchase totals =	$805.05		$883.5001	$883.49	$883.50	$883.50