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	$208.86	9.189%	$228.0521	$228.05	$228.05	$228.10
Purchase #2	$143.41	5.786%	$151.7077	$151.71	$151.70	$151.70
Purchase #3	$119.29	3.464%	$123.4222	$123.42	$123.40	$123.40
Purchase #4	$241.77	3.210%	$249.5308	$249.53	$249.55	$249.50
Purchase #5	$176.39	6.171%	$187.275	$187.28	$187.30	$187.30
Purchase #6	$191.56	3.770%	$198.7818	$198.78	$198.80	$198.80
Purchase #7	$30.68	4.491%	$32.0578	$32.06	$32.05	$32.10
7 purchase totals =	$1,111.96		$1,170.8274	$1,170.83	$1,170.85	$1,170.90