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	$62.50	7.449%	$67.1556	$67.16	$67.15	$67.20
Purchase #2	$132.37	7.563%	$142.3811	$142.38	$142.40	$142.40
Purchase #3	$59.41	13.704%	$67.5515	$67.55	$67.55	$67.60
Purchase #4	$78.82	4.691%	$82.5174	$82.52	$82.50	$82.50
Purchase #5	$67.30	9.274%	$73.5414	$73.54	$73.55	$73.50
Purchase #6	$45.52	4.482%	$47.5602	$47.56	$47.55	$47.60
Purchase #7	$126.51	8.583%	$137.3684	$137.37	$137.35	$137.40
7 purchase totals =	$572.43		$618.0756	$618.08	$618.05	$618.20