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	$240.65	5.778%	$254.5548	$254.55	$254.55	$254.60
Purchase #2	$139.74	10.445%	$154.3358	$154.34	$154.35	$154.30
Purchase #3	$45.85	12.348%	$51.5116	$51.51	$51.50	$51.50
Purchase #4	$95.81	3.153%	$98.8309	$98.83	$98.85	$98.80
Purchase #5	$246.76	13.701%	$280.5686	$280.57	$280.55	$280.60
Purchase #6	$77.49	13.150%	$87.6799	$87.68	$87.70	$87.70
Purchase #7	$116.73	5.831%	$123.5365	$123.54	$123.55	$123.50
7 purchase totals =	$963.03		$1,051.0181	$1,051.02	$1,051.05	$1,051.00