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	$66.26	5.434%	$69.8606	$69.86	$69.85	$69.90
Purchase #2	$177.44	10.694%	$196.4154	$196.42	$196.40	$196.40
Purchase #3	$186.72	9.536%	$204.5256	$204.53	$204.55	$204.50
Purchase #4	$18.52	10.520%	$20.4683	$20.47	$20.45	$20.50
Purchase #5	$76.55	13.351%	$86.7702	$86.77	$86.75	$86.80
Purchase #6	$162.95	10.119%	$179.4389	$179.44	$179.45	$179.40
Purchase #7	$225.90	13.163%	$255.6352	$255.64	$255.65	$255.60
7 purchase totals =	$914.34		$1,013.1142	$1,013.13	$1,013.10	$1,013.10