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	$151.84	8.409%	$164.6082	$164.61	$164.60	$164.60
Purchase #2	$117.41	5.373%	$123.7184	$123.72	$123.70	$123.70
Purchase #3	$94.39	4.762%	$98.8849	$98.88	$98.90	$98.90
Purchase #4	$76.62	8.248%	$82.9396	$82.94	$82.95	$82.90
Purchase #5	$215.48	11.522%	$240.3076	$240.31	$240.30	$240.30
Purchase #6	$64.25	5.493%	$67.7793	$67.78	$67.80	$67.80
Purchase #7	$17.84	9.781%	$19.5849	$19.58	$19.60	$19.60
7 purchase totals =	$737.83		$797.8229	$797.82	$797.85	$797.80