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	$63.88	13.238%	$72.3364	$72.34	$72.35	$72.30
Purchase #2	$75.43	8.800%	$82.0678	$82.07	$82.05	$82.10
Purchase #3	$19.96	7.482%	$21.4534	$21.45	$21.45	$21.50
Purchase #4	$217.51	13.423%	$246.7064	$246.71	$246.70	$246.70
Purchase #5	$186.33	3.261%	$192.4062	$192.41	$192.40	$192.40
Purchase #6	$232.46	11.409%	$258.9814	$258.98	$259.00	$259.00
Purchase #7	$133.88	13.438%	$151.8708	$151.87	$151.85	$151.90
7 purchase totals =	$929.45		$1,025.8224	$1,025.83	$1,025.80	$1,025.90