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	$38.60	6.256%	$41.0148	$41.01	$41.00	$41.00
Purchase #2	$96.96	13.622%	$110.1679	$110.17	$110.15	$110.20
Purchase #3	$90.71	7.435%	$97.4543	$97.45	$97.45	$97.50
Purchase #4	$82.89	8.356%	$89.8163	$89.82	$89.80	$89.80
Purchase #5	$138.71	10.399%	$153.1345	$153.13	$153.15	$153.10
Purchase #6	$16.61	11.507%	$18.5213	$18.52	$18.50	$18.50
Purchase #7	$208.42	4.358%	$217.5029	$217.50	$217.50	$217.50
7 purchase totals =	$672.90		$727.6120	$727.60	$727.55	$727.60