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	$176.38	3.672%	$182.8567	$182.86	$182.85	$182.90
Purchase #2	$74.68	4.858%	$78.308	$78.31	$78.30	$78.30
Purchase #3	$162.64	9.305%	$177.7737	$177.77	$177.75	$177.80
Purchase #4	$78.66	10.451%	$86.8808	$86.88	$86.90	$86.90
Purchase #5	$73.64	12.170%	$82.602	$82.60	$82.60	$82.60
Purchase #6	$212.59	8.846%	$231.3957	$231.40	$231.40	$231.40
Purchase #7	$120.89	13.853%	$137.6369	$137.64	$137.65	$137.60
7 purchase totals =	$899.48		$977.4538	$977.46	$977.45	$977.50