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	$21.64	5.363%	$22.8006	$22.80	$22.80	$22.80
Purchase #2	$132.35	13.367%	$150.0412	$150.04	$150.05	$150.00
Purchase #3	$209.58	12.545%	$235.8718	$235.87	$235.85	$235.90
Purchase #4	$186.58	5.481%	$196.8064	$196.81	$196.80	$196.80
Purchase #5	$90.38	11.365%	$100.6517	$100.65	$100.65	$100.70
Purchase #6	$107.74	6.270%	$114.4953	$114.50	$114.50	$114.50
Purchase #7	$177.75	7.565%	$191.1968	$191.20	$191.20	$191.20
7 purchase totals =	$926.02		$1,011.8638	$1,011.87	$1,011.85	$1,011.90