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	$31.81	6.431%	$33.8557	$33.86	$33.85	$33.90
Purchase #2	$164.68	12.713%	$185.6158	$185.62	$185.60	$185.60
Purchase #3	$72.36	8.767%	$78.7038	$78.70	$78.70	$78.70
Purchase #4	$169.75	9.678%	$186.1784	$186.18	$186.20	$186.20
Purchase #5	$62.49	8.449%	$67.7698	$67.77	$67.75	$67.80
Purchase #6	$20.34	4.496%	$21.2545	$21.25	$21.25	$21.30
Purchase #7	$187.33	13.535%	$212.6851	$212.69	$212.70	$212.70
7 purchase totals =	$708.76		$786.0631	$786.07	$786.05	$786.20