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	$145.25	5.392%	$153.0819	$153.08	$153.10	$153.10
Purchase #2	$246.39	13.763%	$280.3007	$280.30	$280.30	$280.30
Purchase #3	$32.31	6.693%	$34.4725	$34.47	$34.45	$34.50
Purchase #4	$48.33	11.432%	$53.8551	$53.86	$53.85	$53.90
Purchase #5	$128.82	12.759%	$145.2561	$145.26	$145.25	$145.30
Purchase #6	$206.35	9.382%	$225.7098	$225.71	$225.70	$225.70
Purchase #7	$179.93	4.124%	$187.3503	$187.35	$187.35	$187.40
7 purchase totals =	$987.38		$1,080.0264	$1,080.03	$1,080.00	$1,080.20