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	$86.42	11.208%	$96.106	$96.11	$96.10	$96.10
Purchase #2	$15.96	12.551%	$17.9631	$17.96	$17.95	$18.00
Purchase #3	$45.50	9.667%	$49.8985	$49.90	$49.90	$49.90
Purchase #4	$55.60	7.730%	$59.8979	$59.90	$59.90	$59.90
Purchase #5	$158.59	11.106%	$176.203	$176.20	$176.20	$176.20
Purchase #6	$20.83	3.767%	$21.6147	$21.61	$21.60	$21.60
Purchase #7	$90.76	5.225%	$95.5022	$95.50	$95.50	$95.50
7 purchase totals =	$473.66		$517.1854	$517.18	$517.15	$517.20