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	$132.80	9.522%	$145.4452	$145.45	$145.45	$145.40
Purchase #2	$246.83	13.740%	$280.7444	$280.74	$280.75	$280.70
Purchase #3	$103.77	7.690%	$111.7499	$111.75	$111.75	$111.70
Purchase #4	$30.70	10.529%	$33.9324	$33.93	$33.95	$33.90
Purchase #5	$102.94	6.295%	$109.4201	$109.42	$109.40	$109.40
Purchase #6	$123.80	10.741%	$137.0974	$137.10	$137.10	$137.10
Purchase #7	$97.34	12.853%	$109.8511	$109.85	$109.85	$109.90
7 purchase totals =	$838.18		$928.2405	$928.24	$928.25	$928.10