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	$38.96	7.503%	$41.8832	$41.88	$41.90	$41.90
Purchase #2	$114.67	7.847%	$123.6682	$123.67	$123.65	$123.70
Purchase #3	$61.60	6.321%	$65.4937	$65.49	$65.50	$65.50
Purchase #4	$196.98	9.171%	$215.045	$215.05	$215.05	$215.00
Purchase #5	$121.93	3.693%	$126.4329	$126.43	$126.45	$126.40
Purchase #6	$89.54	13.536%	$101.6601	$101.66	$101.65	$101.70
Purchase #7	$27.51	6.329%	$29.2511	$29.25	$29.25	$29.30
7 purchase totals =	$651.19		$703.4342	$703.43	$703.45	$703.50