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	$104.83	10.576%	$115.9168	$115.92	$115.90	$115.90
Purchase #2	$127.73	12.793%	$144.0705	$144.07	$144.05	$144.10
Purchase #3	$153.59	4.771%	$160.9178	$160.92	$160.90	$160.90
Purchase #4	$189.83	10.137%	$209.0731	$209.07	$209.05	$209.10
Purchase #5	$160.96	12.670%	$181.3536	$181.35	$181.35	$181.40
Purchase #6	$112.85	9.252%	$123.2909	$123.29	$123.30	$123.30
Purchase #7	$237.38	3.271%	$245.1447	$245.14	$245.15	$245.10
7 purchase totals =	$1,087.17		$1,179.7674	$1,179.76	$1,179.70	$1,179.80