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	$72.43	13.150%	$81.9545	$81.95	$81.95	$82.00
Purchase #2	$208.71	7.526%	$224.4175	$224.42	$224.40	$224.40
Purchase #3	$122.31	3.236%	$126.268	$126.27	$126.25	$126.30
Purchase #4	$175.55	11.805%	$196.2737	$196.27	$196.25	$196.30
Purchase #5	$68.89	13.279%	$78.0379	$78.04	$78.05	$78.00
Purchase #6	$95.86	9.182%	$104.6619	$104.66	$104.65	$104.70
Purchase #7	$27.88	7.247%	$29.9005	$29.90	$29.90	$29.90
7 purchase totals =	$771.63		$841.5140	$841.51	$841.45	$841.60