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	$115.77	13.493%	$131.3908	$131.39	$131.40	$131.40
Purchase #2	$146.96	13.306%	$166.5145	$166.51	$166.50	$166.50
Purchase #3	$196.39	13.750%	$223.3936	$223.39	$223.40	$223.40
Purchase #4	$45.84	11.749%	$51.2257	$51.23	$51.25	$51.20
Purchase #5	$112.51	5.613%	$118.8252	$118.83	$118.85	$118.80
Purchase #6	$210.54	3.477%	$217.8605	$217.86	$217.85	$217.90
Purchase #7	$235.98	7.398%	$253.4378	$253.44	$253.45	$253.40
7 purchase totals =	$1,063.99		$1,162.6481	$1,162.65	$1,162.70	$1,162.60