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	$86.92	4.105%	$90.4881	$90.49	$90.50	$90.50
Purchase #2	$12.56	8.767%	$13.6611	$13.66	$13.65	$13.70
Purchase #3	$205.99	4.442%	$215.1401	$215.14	$215.15	$215.10
Purchase #4	$39.53	5.131%	$41.5583	$41.56	$41.55	$41.60
Purchase #5	$164.70	10.124%	$181.3742	$181.37	$181.35	$181.40
Purchase #6	$233.70	13.207%	$264.5648	$264.56	$264.55	$264.60
Purchase #7	$177.42	12.115%	$198.9144	$198.91	$198.90	$198.90
7 purchase totals =	$920.82		$1,005.7010	$1,005.69	$1,005.65	$1,005.80