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	$197.85	12.168%	$221.9244	$221.92	$221.90	$221.90
Purchase #2	$49.34	4.495%	$51.5578	$51.56	$51.55	$51.60
Purchase #3	$65.75	10.416%	$72.5985	$72.60	$72.60	$72.60
Purchase #4	$187.68	11.126%	$208.5613	$208.56	$208.55	$208.60
Purchase #5	$32.27	3.226%	$33.311	$33.31	$33.30	$33.30
Purchase #6	$240.56	6.407%	$255.9727	$255.97	$255.95	$256.00
Purchase #7	$77.36	12.362%	$86.9232	$86.92	$86.90	$86.90
7 purchase totals =	$850.81		$930.8489	$930.84	$930.75	$930.90