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	$71.63	9.526%	$78.4535	$78.45	$78.45	$78.50
Purchase #2	$184.35	13.282%	$208.8354	$208.84	$208.85	$208.80
Purchase #3	$131.65	4.656%	$137.7796	$137.78	$137.80	$137.80
Purchase #4	$126.52	12.493%	$142.3261	$142.33	$142.35	$142.30
Purchase #5	$90.87	4.507%	$94.9655	$94.97	$94.95	$95.00
Purchase #6	$200.66	11.807%	$224.3519	$224.35	$224.35	$224.40
Purchase #7	$89.26	9.314%	$97.5737	$97.57	$97.55	$97.60
7 purchase totals =	$894.94		$984.2857	$984.29	$984.30	$984.40