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	$122.25	12.467%	$137.4909	$137.49	$137.50	$137.50
Purchase #2	$208.91	4.292%	$217.8764	$217.88	$217.90	$217.90
Purchase #3	$44.81	11.555%	$49.9878	$49.99	$50.00	$50.00
Purchase #4	$126.51	8.550%	$137.3266	$137.33	$137.35	$137.30
Purchase #5	$242.66	9.558%	$265.8534	$265.85	$265.85	$265.90
Purchase #6	$68.66	5.551%	$72.4713	$72.47	$72.45	$72.50
Purchase #7	$189.53	12.653%	$213.5112	$213.51	$213.50	$213.50
7 purchase totals =	$1,003.33		$1,094.5176	$1,094.52	$1,094.55	$1,094.60