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	$35.92	3.525%	$37.1862	$37.19	$37.20	$37.20
Purchase #2	$14.25	4.565%	$14.9005	$14.90	$14.90	$14.90
Purchase #3	$120.70	5.110%	$126.8678	$126.87	$126.85	$126.90
Purchase #4	$122.92	3.223%	$126.8817	$126.88	$126.90	$126.90
Purchase #5	$40.47	8.478%	$43.901	$43.90	$43.90	$43.90
Purchase #6	$119.81	9.797%	$131.5478	$131.55	$131.55	$131.50
Purchase #7	$117.48	5.422%	$123.8498	$123.85	$123.85	$123.80
7 purchase totals =	$571.55		$605.1348	$605.14	$605.15	$605.10