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	$105.50	10.127%	$116.184	$116.18	$116.20	$116.20
Purchase #2	$228.81	3.550%	$236.9328	$236.93	$236.95	$236.90
Purchase #3	$27.27	3.806%	$28.3079	$28.31	$28.30	$28.30
Purchase #4	$85.68	3.611%	$88.7739	$88.77	$88.75	$88.80
Purchase #5	$96.35	8.778%	$104.8076	$104.81	$104.80	$104.80
Purchase #6	$97.72	9.140%	$106.6516	$106.65	$106.65	$106.70
Purchase #7	$100.98	4.801%	$105.828	$105.83	$105.85	$105.80
7 purchase totals =	$742.31		$787.4858	$787.48	$787.50	$787.50