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	$99.91	8.669%	$108.5712	$108.57	$108.55	$108.60
Purchase #2	$140.88	10.661%	$155.8992	$155.90	$155.90	$155.90
Purchase #3	$185.42	12.447%	$208.4992	$208.50	$208.50	$208.50
Purchase #4	$111.25	4.119%	$115.8324	$115.83	$115.85	$115.80
Purchase #5	$192.31	10.591%	$212.6776	$212.68	$212.70	$212.70
Purchase #6	$77.78	6.155%	$82.5674	$82.57	$82.55	$82.60
Purchase #7	$196.31	3.371%	$202.9276	$202.93	$202.95	$202.90
7 purchase totals =	$1,003.86		$1,086.9746	$1,086.98	$1,087.00	$1,087.00