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	$241.26	5.227%	$253.8707	$253.87	$253.85	$253.90
Purchase #2	$18.67	6.329%	$19.8516	$19.85	$19.85	$19.90
Purchase #3	$219.57	5.348%	$231.3126	$231.31	$231.30	$231.30
Purchase #4	$245.31	10.794%	$271.7888	$271.79	$271.80	$271.80
Purchase #5	$95.25	13.724%	$108.3221	$108.32	$108.30	$108.30
Purchase #6	$216.29	10.290%	$238.5462	$238.55	$238.55	$238.50
Purchase #7	$77.32	6.426%	$82.2886	$82.29	$82.30	$82.30
7 purchase totals =	$1,113.67		$1,205.9806	$1,205.98	$1,205.95	$1,206.00