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	$59.27	12.354%	$66.5922	$66.59	$66.60	$66.60
Purchase #2	$195.68	6.526%	$208.4501	$208.45	$208.45	$208.50
Purchase #3	$231.39	4.417%	$241.6105	$241.61	$241.60	$241.60
Purchase #4	$24.36	12.277%	$27.3507	$27.35	$27.35	$27.40
Purchase #5	$121.48	4.492%	$126.9369	$126.94	$126.95	$126.90
Purchase #6	$74.40	10.623%	$82.3035	$82.30	$82.30	$82.30
Purchase #7	$161.56	13.203%	$182.8908	$182.89	$182.90	$182.90
7 purchase totals =	$868.14		$936.1347	$936.13	$936.15	$936.20