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	$86.85	11.185%	$96.5642	$96.56	$96.55	$96.60
Purchase #2	$52.46	7.818%	$56.5613	$56.56	$56.55	$56.60
Purchase #3	$39.50	10.393%	$43.6052	$43.61	$43.60	$43.60
Purchase #4	$114.94	4.664%	$120.3008	$120.30	$120.30	$120.30
Purchase #5	$132.51	3.351%	$136.9504	$136.95	$136.95	$137.00
Purchase #6	$125.40	4.824%	$131.4493	$131.45	$131.45	$131.40
Purchase #7	$219.79	10.125%	$242.0437	$242.04	$242.05	$242.00
7 purchase totals =	$771.45		$827.4749	$827.47	$827.45	$827.50