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	$202.81	12.371%	$227.8996	$227.90	$227.90	$227.90
Purchase #2	$14.41	3.829%	$14.9618	$14.96	$14.95	$15.00
Purchase #3	$54.46	13.660%	$61.8992	$61.90	$61.90	$61.90
Purchase #4	$234.85	13.709%	$267.0456	$267.05	$267.05	$267.00
Purchase #5	$216.76	11.421%	$241.5162	$241.52	$241.50	$241.50
Purchase #6	$214.75	3.661%	$222.612	$222.61	$222.60	$222.60
Purchase #7	$43.49	3.659%	$45.0813	$45.08	$45.10	$45.10
7 purchase totals =	$981.53		$1,081.0157	$1,081.02	$1,081.00	$1,081.00