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	$86.40	3.264%	$89.2201	$89.22	$89.20	$89.20
Purchase #2	$41.59	13.845%	$47.3481	$47.35	$47.35	$47.30
Purchase #3	$123.93	10.738%	$137.2376	$137.24	$137.25	$137.20
Purchase #4	$227.89	12.135%	$255.5445	$255.54	$255.55	$255.50
Purchase #5	$184.97	7.389%	$198.6374	$198.64	$198.65	$198.60
Purchase #6	$105.26	11.232%	$117.0828	$117.08	$117.10	$117.10
Purchase #7	$210.89	12.490%	$237.2302	$237.23	$237.25	$237.20
7 purchase totals =	$980.93		$1,082.3007	$1,082.30	$1,082.35	$1,082.10