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	$144.38	8.141%	$156.134	$156.13	$156.15	$156.10
Purchase #2	$92.83	10.554%	$102.6273	$102.63	$102.65	$102.60
Purchase #3	$91.57	12.592%	$103.1005	$103.10	$103.10	$103.10
Purchase #4	$225.32	5.478%	$237.663	$237.66	$237.65	$237.70
Purchase #5	$163.82	9.544%	$179.455	$179.46	$179.45	$179.50
Purchase #6	$87.25	10.600%	$96.4985	$96.50	$96.50	$96.50
Purchase #7	$90.36	13.858%	$102.8821	$102.88	$102.90	$102.90
7 purchase totals =	$895.53		$978.3604	$978.36	$978.40	$978.40