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	$222.52	5.443%	$234.6318	$234.63	$234.65	$234.60
Purchase #2	$157.41	4.212%	$164.0401	$164.04	$164.05	$164.00
Purchase #3	$126.75	12.493%	$142.5849	$142.58	$142.60	$142.60
Purchase #4	$156.76	7.703%	$168.8352	$168.84	$168.85	$168.80
Purchase #5	$129.81	9.693%	$142.3925	$142.39	$142.40	$142.40
Purchase #6	$105.69	10.164%	$116.4323	$116.43	$116.45	$116.40
Purchase #7	$201.75	8.446%	$218.7898	$218.79	$218.80	$218.80
7 purchase totals =	$1,100.69		$1,187.7066	$1,187.70	$1,187.80	$1,187.60