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	$226.82	3.874%	$235.607	$235.61	$235.60	$235.60
Purchase #2	$82.62	9.729%	$90.6581	$90.66	$90.65	$90.70
Purchase #3	$40.63	6.281%	$43.182	$43.18	$43.20	$43.20
Purchase #4	$94.64	5.176%	$99.5386	$99.54	$99.55	$99.50
Purchase #5	$162.58	4.301%	$169.5726	$169.57	$169.55	$169.60
Purchase #6	$214.92	7.615%	$231.2862	$231.29	$231.30	$231.30
Purchase #7	$82.94	8.236%	$89.7709	$89.77	$89.75	$89.80
7 purchase totals =	$905.15		$959.6154	$959.62	$959.60	$959.70