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	$130.56	11.733%	$145.8786	$145.88	$145.90	$145.90
Purchase #2	$190.67	5.331%	$200.8346	$200.83	$200.85	$200.80
Purchase #3	$233.80	6.739%	$249.5558	$249.56	$249.55	$249.60
Purchase #4	$11.90	5.159%	$12.5139	$12.51	$12.50	$12.50
Purchase #5	$103.69	11.534%	$115.6496	$115.65	$115.65	$115.60
Purchase #6	$87.54	5.616%	$92.4562	$92.46	$92.45	$92.50
Purchase #7	$220.39	7.831%	$237.6487	$237.65	$237.65	$237.60
7 purchase totals =	$978.55		$1,054.5374	$1,054.54	$1,054.55	$1,054.50