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	$43.45	13.632%	$49.3731	$49.37	$49.35	$49.40
Purchase #2	$32.81	3.678%	$34.0168	$34.02	$34.00	$34.00
Purchase #3	$250.79	10.273%	$276.5537	$276.55	$276.55	$276.60
Purchase #4	$182.42	4.469%	$190.5723	$190.57	$190.55	$190.60
Purchase #5	$192.52	5.209%	$202.5484	$202.55	$202.55	$202.50
Purchase #6	$217.93	7.355%	$233.9588	$233.96	$233.95	$234.00
Purchase #7	$89.41	11.648%	$99.8245	$99.82	$99.80	$99.80
7 purchase totals =	$1,009.33		$1,086.8476	$1,086.84	$1,086.75	$1,086.90