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	$90.59	6.217%	$96.222	$96.22	$96.20	$96.20
Purchase #2	$24.25	6.529%	$25.8333	$25.83	$25.85	$25.80
Purchase #3	$47.92	12.716%	$54.0135	$54.01	$54.00	$54.00
Purchase #4	$28.68	3.233%	$29.6072	$29.61	$29.60	$29.60
Purchase #5	$20.92	4.366%	$21.8334	$21.83	$21.85	$21.80
Purchase #6	$207.92	4.379%	$217.0248	$217.02	$217.00	$217.00
Purchase #7	$119.88	13.855%	$136.4894	$136.49	$136.50	$136.50
7 purchase totals =	$540.16		$581.0236	$581.01	$581.00	$580.90