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	$180.62	6.492%	$192.3459	$192.35	$192.35	$192.30
Purchase #2	$179.54	13.805%	$204.3255	$204.33	$204.35	$204.30
Purchase #3	$100.77	10.565%	$111.4164	$111.42	$111.40	$111.40
Purchase #4	$127.64	8.788%	$138.857	$138.86	$138.85	$138.90
Purchase #5	$57.39	10.371%	$63.3419	$63.34	$63.35	$63.30
Purchase #6	$42.46	8.484%	$46.0623	$46.06	$46.05	$46.10
Purchase #7	$217.67	11.866%	$243.4987	$243.50	$243.50	$243.50
7 purchase totals =	$906.09		$999.8477	$999.86	$999.85	$999.80