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	$97.94	12.809%	$110.4851	$110.49	$110.50	$110.50
Purchase #2	$139.32	5.189%	$146.5493	$146.55	$146.55	$146.50
Purchase #3	$231.60	9.264%	$253.0554	$253.06	$253.05	$253.10
Purchase #4	$198.56	6.515%	$211.4962	$211.50	$211.50	$211.50
Purchase #5	$171.76	8.670%	$186.6516	$186.65	$186.65	$186.70
Purchase #6	$145.74	4.219%	$151.8888	$151.89	$151.90	$151.90
Purchase #7	$56.37	12.408%	$63.3644	$63.36	$63.35	$63.40
7 purchase totals =	$1,041.29		$1,123.4908	$1,123.50	$1,123.50	$1,123.60