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	$126.38	8.841%	$137.5533	$137.55	$137.55	$137.60
Purchase #2	$91.55	13.802%	$104.1857	$104.19	$104.20	$104.20
Purchase #3	$9.52	10.177%	$10.4889	$10.49	$10.50	$10.50
Purchase #4	$206.88	5.350%	$217.9481	$217.95	$217.95	$217.90
Purchase #5	$37.85	12.782%	$42.688	$42.69	$42.70	$42.70
Purchase #6	$100.25	12.259%	$112.5396	$112.54	$112.55	$112.50
Purchase #7	$74.84	8.830%	$81.4484	$81.45	$81.45	$81.40
7 purchase totals =	$647.27		$706.8520	$706.86	$706.90	$706.80