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	$59.93	7.699%	$64.544	$64.54	$64.55	$64.50
Purchase #2	$56.32	7.394%	$60.4843	$60.48	$60.50	$60.50
Purchase #3	$46.29	10.797%	$51.2879	$51.29	$51.30	$51.30
Purchase #4	$245.97	5.758%	$260.133	$260.13	$260.15	$260.10
Purchase #5	$241.88	5.671%	$255.597	$255.60	$255.60	$255.60
Purchase #6	$172.81	9.326%	$188.9263	$188.93	$188.95	$188.90
Purchase #7	$104.28	5.321%	$109.8287	$109.83	$109.85	$109.80
7 purchase totals =	$927.48		$990.8012	$990.80	$990.90	$990.70