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	$79.90	7.141%	$85.6057	$85.61	$85.60	$85.60
Purchase #2	$123.43	11.111%	$137.1443	$137.14	$137.15	$137.10
Purchase #3	$129.88	6.735%	$138.6274	$138.63	$138.65	$138.60
Purchase #4	$83.52	3.742%	$86.6453	$86.65	$86.65	$86.60
Purchase #5	$137.64	10.791%	$152.4927	$152.49	$152.50	$152.50
Purchase #6	$19.56	6.627%	$20.8562	$20.86	$20.85	$20.90
Purchase #7	$89.88	5.212%	$94.5645	$94.56	$94.55	$94.60
7 purchase totals =	$663.81		$715.9361	$715.94	$715.95	$715.90