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	$168.71	7.163%	$180.7947	$180.79	$180.80	$180.80
Purchase #2	$160.84	4.715%	$168.4236	$168.42	$168.40	$168.40
Purchase #3	$92.80	3.828%	$96.3524	$96.35	$96.35	$96.40
Purchase #4	$100.50	12.685%	$113.2484	$113.25	$113.25	$113.20
Purchase #5	$67.89	12.683%	$76.5005	$76.50	$76.50	$76.50
Purchase #6	$175.94	13.141%	$199.0603	$199.06	$199.05	$199.10
Purchase #7	$109.51	12.610%	$123.3192	$123.32	$123.30	$123.30
7 purchase totals =	$876.19		$957.6991	$957.69	$957.65	$957.70