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	$39.96	9.211%	$43.6407	$43.64	$43.65	$43.60
Purchase #2	$211.45	5.863%	$223.8473	$223.85	$223.85	$223.80
Purchase #3	$106.85	11.108%	$118.7189	$118.72	$118.70	$118.70
Purchase #4	$97.33	4.388%	$101.6008	$101.60	$101.60	$101.60
Purchase #5	$183.67	6.859%	$196.2679	$196.27	$196.25	$196.30
Purchase #6	$215.44	11.854%	$240.9783	$240.98	$241.00	$241.00
Purchase #7	$162.41	8.842%	$176.7703	$176.77	$176.75	$176.80
7 purchase totals =	$1,017.11		$1,101.8242	$1,101.83	$1,101.80	$1,101.80