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	$69.51	10.577%	$76.8621	$76.86	$76.85	$76.90
Purchase #2	$23.54	7.833%	$25.3839	$25.38	$25.40	$25.40
Purchase #3	$137.67	10.692%	$152.3897	$152.39	$152.40	$152.40
Purchase #4	$181.70	9.304%	$198.6054	$198.61	$198.60	$198.60
Purchase #5	$56.90	12.331%	$63.9163	$63.92	$63.90	$63.90
Purchase #6	$35.75	3.155%	$36.8779	$36.88	$36.90	$36.90
Purchase #7	$59.65	4.826%	$62.5287	$62.53	$62.55	$62.50
7 purchase totals =	$564.72		$616.5640	$616.57	$616.60	$616.60