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	$180.95	11.316%	$201.4263	$201.43	$201.45	$201.40
Purchase #2	$63.93	9.326%	$69.8921	$69.89	$69.90	$69.90
Purchase #3	$92.53	4.450%	$96.6476	$96.65	$96.65	$96.60
Purchase #4	$59.59	12.245%	$66.8868	$66.89	$66.90	$66.90
Purchase #5	$80.47	3.785%	$83.5158	$83.52	$83.50	$83.50
Purchase #6	$110.85	11.792%	$123.9214	$123.92	$123.90	$123.90
Purchase #7	$168.35	10.811%	$186.5503	$186.55	$186.55	$186.60
7 purchase totals =	$756.67		$828.8403	$828.85	$828.85	$828.80