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	$140.55	9.450%	$153.832	$153.83	$153.85	$153.80
Purchase #2	$96.52	9.147%	$105.3487	$105.35	$105.35	$105.30
Purchase #3	$248.71	12.811%	$280.5722	$280.57	$280.55	$280.60
Purchase #4	$25.87	7.277%	$27.7526	$27.75	$27.75	$27.80
Purchase #5	$57.43	13.690%	$65.2922	$65.29	$65.30	$65.30
Purchase #6	$57.30	8.401%	$62.1138	$62.11	$62.10	$62.10
Purchase #7	$55.79	9.162%	$60.9015	$60.90	$60.90	$60.90
7 purchase totals =	$682.17		$755.8130	$755.80	$755.80	$755.80