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	$80.98	3.661%	$83.9447	$83.94	$83.95	$83.90
Purchase #2	$202.85	7.134%	$217.3213	$217.32	$217.30	$217.30
Purchase #3	$174.80	10.356%	$192.9023	$192.90	$192.90	$192.90
Purchase #4	$119.99	5.435%	$126.5115	$126.51	$126.50	$126.50
Purchase #5	$87.72	13.387%	$99.4631	$99.46	$99.45	$99.50
Purchase #6	$156.81	7.320%	$168.2885	$168.29	$168.30	$168.30
Purchase #7	$203.56	6.752%	$217.3044	$217.30	$217.30	$217.30
7 purchase totals =	$1,026.71		$1,105.7358	$1,105.72	$1,105.70	$1,105.70