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	$41.92	3.826%	$43.5239	$43.52	$43.50	$43.50
Purchase #2	$173.37	5.507%	$182.9175	$182.92	$182.90	$182.90
Purchase #3	$112.84	12.614%	$127.0736	$127.07	$127.05	$127.10
Purchase #4	$19.59	10.650%	$21.6763	$21.68	$21.70	$21.70
Purchase #5	$53.40	5.509%	$56.3418	$56.34	$56.35	$56.30
Purchase #6	$236.42	8.137%	$255.6575	$255.66	$255.65	$255.70
Purchase #7	$114.94	8.215%	$124.3823	$124.38	$124.40	$124.40
7 purchase totals =	$752.48		$811.5729	$811.57	$811.55	$811.60