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	$239.89	9.160%	$261.8639	$261.86	$261.85	$261.90
Purchase #2	$56.91	8.303%	$61.6352	$61.64	$61.65	$61.60
Purchase #3	$86.51	11.598%	$96.5434	$96.54	$96.55	$96.50
Purchase #4	$160.93	4.821%	$168.6884	$168.69	$168.70	$168.70
Purchase #5	$148.74	10.618%	$164.5332	$164.53	$164.55	$164.50
Purchase #6	$103.86	10.678%	$114.9502	$114.95	$114.95	$115.00
Purchase #7	$36.94	4.156%	$38.4752	$38.48	$38.50	$38.50
7 purchase totals =	$833.78		$906.6895	$906.69	$906.75	$906.70