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	$11.42	7.140%	$12.2354	$12.24	$12.25	$12.20
Purchase #2	$30.48	5.144%	$32.0479	$32.05	$32.05	$32.00
Purchase #3	$107.79	6.791%	$115.11	$115.11	$115.10	$115.10
Purchase #4	$111.83	10.132%	$123.1606	$123.16	$123.15	$123.20
Purchase #5	$118.95	12.607%	$133.946	$133.95	$133.95	$133.90
Purchase #6	$59.83	10.224%	$65.947	$65.95	$65.95	$65.90
Purchase #7	$193.88	3.291%	$200.2606	$200.26	$200.25	$200.30
7 purchase totals =	$634.18		$682.7075	$682.72	$682.70	$682.60