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	$78.35	10.403%	$86.5008	$86.50	$86.50	$86.50
Purchase #2	$83.63	13.412%	$94.8465	$94.85	$94.85	$94.80
Purchase #3	$61.29	3.184%	$63.2415	$63.24	$63.25	$63.20
Purchase #4	$10.28	9.111%	$11.2166	$11.22	$11.20	$11.20
Purchase #5	$63.63	13.871%	$72.4561	$72.46	$72.45	$72.50
Purchase #6	$210.29	10.278%	$231.9036	$231.90	$231.90	$231.90
Purchase #7	$154.40	10.411%	$170.4746	$170.47	$170.45	$170.50
7 purchase totals =	$661.87		$730.6397	$730.64	$730.60	$730.60