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	$84.51	3.141%	$87.1645	$87.16	$87.15	$87.20
Purchase #2	$99.92	4.524%	$104.4404	$104.44	$104.45	$104.40
Purchase #3	$175.83	13.337%	$199.2804	$199.28	$199.30	$199.30
Purchase #4	$96.79	5.208%	$101.8308	$101.83	$101.85	$101.80
Purchase #5	$48.86	13.749%	$55.5778	$55.58	$55.60	$55.60
Purchase #6	$81.84	3.184%	$84.4458	$84.45	$84.45	$84.40
Purchase #7	$86.81	4.614%	$90.8154	$90.82	$90.80	$90.80
7 purchase totals =	$674.56		$723.5551	$723.56	$723.60	$723.50