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	$93.69	9.757%	$102.8313	$102.83	$102.85	$102.80
Purchase #2	$177.73	10.447%	$196.2975	$196.30	$196.30	$196.30
Purchase #3	$176.39	3.120%	$181.8934	$181.89	$181.90	$181.90
Purchase #4	$73.98	8.357%	$80.1625	$80.16	$80.15	$80.20
Purchase #5	$80.45	12.552%	$90.5481	$90.55	$90.55	$90.50
Purchase #6	$51.62	8.299%	$55.9039	$55.90	$55.90	$55.90
Purchase #7	$90.96	3.547%	$94.1864	$94.19	$94.20	$94.20
7 purchase totals =	$744.82		$801.8231	$801.82	$801.85	$801.80