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	$96.50	9.480%	$105.6482	$105.65	$105.65	$105.60
Purchase #2	$10.29	9.710%	$11.2892	$11.29	$11.30	$11.30
Purchase #3	$171.70	12.193%	$192.6354	$192.64	$192.65	$192.60
Purchase #4	$98.93	12.276%	$111.0746	$111.07	$111.05	$111.10
Purchase #5	$169.48	10.733%	$187.6703	$187.67	$187.65	$187.70
Purchase #6	$17.53	6.300%	$18.6344	$18.63	$18.65	$18.60
Purchase #7	$246.78	13.517%	$280.1373	$280.14	$280.15	$280.10
7 purchase totals =	$811.21		$907.0894	$907.09	$907.10	$907.00