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	$239.64	5.798%	$253.5343	$253.53	$253.55	$253.50
Purchase #2	$127.85	13.672%	$145.3297	$145.33	$145.35	$145.30
Purchase #3	$189.47	4.768%	$198.5039	$198.50	$198.50	$198.50
Purchase #4	$127.78	13.326%	$144.808	$144.81	$144.80	$144.80
Purchase #5	$215.82	7.332%	$231.6439	$231.64	$231.65	$231.60
Purchase #6	$28.54	9.103%	$31.138	$31.14	$31.15	$31.10
Purchase #7	$84.31	13.172%	$95.4153	$95.42	$95.40	$95.40
7 purchase totals =	$1,013.41		$1,100.3731	$1,100.37	$1,100.40	$1,100.20