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	$113.89	10.347%	$125.6742	$125.67	$125.65	$125.70
Purchase #2	$151.89	5.265%	$159.887	$159.89	$159.90	$159.90
Purchase #3	$34.48	7.509%	$37.0691	$37.07	$37.05	$37.10
Purchase #4	$46.40	11.137%	$51.5676	$51.57	$51.55	$51.60
Purchase #5	$14.29	3.482%	$14.7876	$14.79	$14.80	$14.80
Purchase #6	$198.93	13.136%	$225.0614	$225.06	$225.05	$225.10
Purchase #7	$139.71	8.287%	$151.2878	$151.29	$151.30	$151.30
7 purchase totals =	$699.59		$765.3347	$765.34	$765.30	$765.50