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	$163.81	7.158%	$175.5355	$175.54	$175.55	$175.50
Purchase #2	$141.62	12.861%	$159.8337	$159.83	$159.85	$159.80
Purchase #3	$142.72	3.556%	$147.7951	$147.80	$147.80	$147.80
Purchase #4	$227.73	12.484%	$256.1598	$256.16	$256.15	$256.20
Purchase #5	$141.42	7.397%	$151.8808	$151.88	$151.90	$151.90
Purchase #6	$97.45	5.572%	$102.8799	$102.88	$102.90	$102.90
Purchase #7	$83.82	9.748%	$91.9908	$91.99	$92.00	$92.00
7 purchase totals =	$998.57		$1,086.0756	$1,086.08	$1,086.15	$1,086.10