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	$36.46	13.737%	$41.4685	$41.47	$41.45	$41.50
Purchase #2	$172.87	13.385%	$196.0086	$196.01	$196.00	$196.00
Purchase #3	$177.83	8.652%	$193.2159	$193.22	$193.20	$193.20
Purchase #4	$232.45	11.792%	$259.8605	$259.86	$259.85	$259.90
Purchase #5	$98.27	5.133%	$103.3142	$103.31	$103.30	$103.30
Purchase #6	$50.84	12.138%	$57.011	$57.01	$57.00	$57.00
Purchase #7	$18.31	6.361%	$19.4747	$19.47	$19.45	$19.50
7 purchase totals =	$787.03		$870.3534	$870.35	$870.25	$870.40