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	$249.40	6.409%	$265.384	$265.38	$265.40	$265.40
Purchase #2	$82.42	7.326%	$88.4581	$88.46	$88.45	$88.50
Purchase #3	$113.37	13.313%	$128.4629	$128.46	$128.45	$128.50
Purchase #4	$171.35	8.577%	$186.0467	$186.05	$186.05	$186.00
Purchase #5	$73.54	12.462%	$82.7046	$82.70	$82.70	$82.70
Purchase #6	$185.36	12.490%	$208.5115	$208.51	$208.50	$208.50
Purchase #7	$171.94	13.657%	$195.4218	$195.42	$195.40	$195.40
7 purchase totals =	$1,047.38		$1,154.9896	$1,154.98	$1,154.95	$1,155.00