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	$162.88	7.785%	$175.5602	$175.56	$175.55	$175.60
Purchase #2	$75.58	13.226%	$85.5762	$85.58	$85.60	$85.60
Purchase #3	$199.54	13.705%	$226.887	$226.89	$226.90	$226.90
Purchase #4	$20.78	3.812%	$21.5721	$21.57	$21.55	$21.60
Purchase #5	$124.41	10.813%	$137.8625	$137.86	$137.85	$137.90
Purchase #6	$139.64	3.315%	$144.2691	$144.27	$144.25	$144.30
Purchase #7	$48.31	7.475%	$51.9212	$51.92	$51.90	$51.90
7 purchase totals =	$771.14		$843.6483	$843.65	$843.60	$843.80