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	$24.30	4.449%	$25.3811	$25.38	$25.40	$25.40
Purchase #2	$23.78	7.145%	$25.4791	$25.48	$25.50	$25.50
Purchase #3	$36.77	10.199%	$40.5202	$40.52	$40.50	$40.50
Purchase #4	$64.83	5.409%	$68.3367	$68.34	$68.35	$68.30
Purchase #5	$76.77	10.592%	$84.9015	$84.90	$84.90	$84.90
Purchase #6	$247.25	13.588%	$280.8463	$280.85	$280.85	$280.80
Purchase #7	$62.71	4.720%	$65.6699	$65.67	$65.65	$65.70
7 purchase totals =	$536.41		$591.1348	$591.14	$591.15	$591.10