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	$40.38	10.330%	$44.5513	$44.55	$44.55	$44.60
Purchase #2	$192.28	12.248%	$215.8305	$215.83	$215.85	$215.80
Purchase #3	$156.35	5.442%	$164.8586	$164.86	$164.85	$164.90
Purchase #4	$81.89	12.155%	$91.8437	$91.84	$91.85	$91.80
Purchase #5	$241.56	11.700%	$269.8225	$269.82	$269.80	$269.80
Purchase #6	$238.29	13.762%	$271.0835	$271.08	$271.10	$271.10
Purchase #7	$179.84	11.187%	$199.9587	$199.96	$199.95	$200.00
7 purchase totals =	$1,130.59		$1,257.9488	$1,257.94	$1,257.95	$1,258.00