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	$184.88	12.739%	$208.4319	$208.43	$208.45	$208.40
Purchase #2	$158.43	13.540%	$179.8814	$179.88	$179.90	$179.90
Purchase #3	$79.34	7.644%	$85.4047	$85.40	$85.40	$85.40
Purchase #4	$56.55	10.462%	$62.4663	$62.47	$62.45	$62.50
Purchase #5	$113.38	7.722%	$122.1352	$122.14	$122.15	$122.10
Purchase #6	$133.76	4.704%	$140.0521	$140.05	$140.05	$140.10
Purchase #7	$241.62	6.314%	$256.8759	$256.88	$256.90	$256.90
7 purchase totals =	$967.96		$1,055.2475	$1,055.25	$1,055.30	$1,055.30