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	$162.58	12.466%	$182.8472	$182.85	$182.85	$182.80
Purchase #2	$135.53	5.458%	$142.9272	$142.93	$142.95	$142.90
Purchase #3	$155.33	13.860%	$176.8587	$176.86	$176.85	$176.90
Purchase #4	$77.93	12.464%	$87.6432	$87.64	$87.65	$87.60
Purchase #5	$118.29	4.704%	$123.8544	$123.85	$123.85	$123.90
Purchase #6	$141.64	9.356%	$154.8918	$154.89	$154.90	$154.90
Purchase #7	$128.91	12.116%	$144.5287	$144.53	$144.55	$144.50
7 purchase totals =	$920.21		$1,013.5512	$1,013.55	$1,013.60	$1,013.50