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	$183.54	8.367%	$198.8968	$198.90	$198.90	$198.90
Purchase #2	$245.64	4.258%	$256.0994	$256.10	$256.10	$256.10
Purchase #3	$51.44	11.582%	$57.3978	$57.40	$57.40	$57.40
Purchase #4	$246.97	6.239%	$262.3785	$262.38	$262.40	$262.40
Purchase #5	$12.73	10.196%	$14.028	$14.03	$14.05	$14.00
Purchase #6	$232.25	10.428%	$256.469	$256.47	$256.45	$256.50
Purchase #7	$176.25	11.620%	$196.7303	$196.73	$196.75	$196.70
7 purchase totals =	$1,148.82		$1,241.9998	$1,242.01	$1,242.05	$1,242.00