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	$139.86	7.643%	$150.5495	$150.55	$150.55	$150.50
Purchase #2	$136.92	11.854%	$153.1505	$153.15	$153.15	$153.20
Purchase #3	$196.79	10.611%	$217.6714	$217.67	$217.65	$217.70
Purchase #4	$225.64	6.305%	$239.8666	$239.87	$239.85	$239.90
Purchase #5	$37.63	7.719%	$40.5347	$40.53	$40.55	$40.50
Purchase #6	$106.91	7.420%	$114.8427	$114.84	$114.85	$114.80
Purchase #7	$89.33	11.304%	$99.4279	$99.43	$99.45	$99.40
7 purchase totals =	$933.08		$1,016.0433	$1,016.04	$1,016.05	$1,016.00