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	$126.71	12.806%	$142.9365	$142.94	$142.95	$142.90
Purchase #2	$213.34	6.561%	$227.3372	$227.34	$227.35	$227.30
Purchase #3	$89.78	5.289%	$94.5285	$94.53	$94.55	$94.50
Purchase #4	$156.25	4.873%	$163.8641	$163.86	$163.85	$163.90
Purchase #5	$188.53	12.713%	$212.4978	$212.50	$212.50	$212.50
Purchase #6	$114.71	7.629%	$123.4612	$123.46	$123.45	$123.50
Purchase #7	$108.83	9.255%	$118.9022	$118.90	$118.90	$118.90
7 purchase totals =	$998.15		$1,083.5275	$1,083.53	$1,083.55	$1,083.50