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	$119.51	6.455%	$127.2244	$127.22	$127.20	$127.20
Purchase #2	$97.84	6.493%	$104.1928	$104.19	$104.20	$104.20
Purchase #3	$118.72	12.748%	$133.8544	$133.85	$133.85	$133.90
Purchase #4	$145.60	13.404%	$165.1162	$165.12	$165.10	$165.10
Purchase #5	$138.59	12.462%	$155.8611	$155.86	$155.85	$155.90
Purchase #6	$144.55	8.123%	$156.2918	$156.29	$156.30	$156.30
Purchase #7	$219.41	5.516%	$231.5127	$231.51	$231.50	$231.50
7 purchase totals =	$984.22		$1,074.0534	$1,074.04	$1,074.00	$1,074.10