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	$177.59	11.850%	$198.6344	$198.63	$198.65	$198.60
Purchase #2	$87.40	10.579%	$96.646	$96.65	$96.65	$96.60
Purchase #3	$27.99	12.480%	$31.4832	$31.48	$31.50	$31.50
Purchase #4	$127.27	13.509%	$144.4629	$144.46	$144.45	$144.50
Purchase #5	$175.85	3.284%	$181.6249	$181.62	$181.60	$181.60
Purchase #6	$171.58	9.114%	$187.2178	$187.22	$187.20	$187.20
Purchase #7	$85.30	13.554%	$96.8616	$96.86	$96.85	$96.90
7 purchase totals =	$852.98		$936.9308	$936.92	$936.90	$936.90