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	$36.39	12.468%	$40.9271	$40.93	$40.95	$40.90
Purchase #2	$207.30	4.135%	$215.8719	$215.87	$215.85	$215.90
Purchase #3	$105.57	5.283%	$111.1473	$111.15	$111.15	$111.10
Purchase #4	$39.42	11.453%	$43.9348	$43.93	$43.95	$43.90
Purchase #5	$115.31	7.492%	$123.949	$123.95	$123.95	$123.90
Purchase #6	$36.38	7.402%	$39.0728	$39.07	$39.05	$39.10
Purchase #7	$88.84	9.411%	$97.2007	$97.20	$97.20	$97.20
7 purchase totals =	$629.21		$672.1036	$672.10	$672.10	$672.00