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	$117.92	12.339%	$132.4701	$132.47	$132.45	$132.50
Purchase #2	$72.67	13.615%	$82.564	$82.56	$82.55	$82.60
Purchase #3	$204.88	8.601%	$222.5017	$222.50	$222.50	$222.50
Purchase #4	$101.40	6.703%	$108.1968	$108.20	$108.20	$108.20
Purchase #5	$195.42	10.546%	$216.029	$216.03	$216.05	$216.00
Purchase #6	$232.45	13.598%	$264.0586	$264.06	$264.05	$264.10
Purchase #7	$198.71	8.642%	$215.8825	$215.88	$215.90	$215.90
7 purchase totals =	$1,123.45		$1,241.7027	$1,241.70	$1,241.70	$1,241.80