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	$219.61	9.671%	$240.8485	$240.85	$240.85	$240.80
Purchase #2	$80.95	8.282%	$87.6543	$87.65	$87.65	$87.70
Purchase #3	$195.64	10.697%	$216.5676	$216.57	$216.55	$216.60
Purchase #4	$191.70	3.393%	$198.2044	$198.20	$198.20	$198.20
Purchase #5	$134.43	6.380%	$143.0066	$143.01	$143.00	$143.00
Purchase #6	$56.35	5.469%	$59.4318	$59.43	$59.45	$59.40
Purchase #7	$142.33	5.455%	$150.0941	$150.09	$150.10	$150.10
7 purchase totals =	$1,021.01		$1,095.8073	$1,095.80	$1,095.80	$1,095.80