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	$142.83	6.168%	$151.6398	$151.64	$151.65	$151.60
Purchase #2	$138.84	13.857%	$158.0791	$158.08	$158.10	$158.10
Purchase #3	$146.87	6.151%	$155.904	$155.90	$155.90	$155.90
Purchase #4	$196.51	13.367%	$222.7775	$222.78	$222.80	$222.80
Purchase #5	$25.96	5.442%	$27.3727	$27.37	$27.35	$27.40
Purchase #6	$179.64	3.845%	$186.5472	$186.55	$186.55	$186.50
Purchase #7	$162.86	9.180%	$177.8105	$177.81	$177.80	$177.80
7 purchase totals =	$993.51		$1,080.1308	$1,080.13	$1,080.15	$1,080.10