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	$156.36	5.745%	$165.3429	$165.34	$165.35	$165.30
Purchase #2	$95.29	13.816%	$108.4553	$108.46	$108.45	$108.50
Purchase #3	$93.89	12.106%	$105.2563	$105.26	$105.25	$105.30
Purchase #4	$237.42	3.748%	$246.3185	$246.32	$246.30	$246.30
Purchase #5	$161.39	12.659%	$181.8204	$181.82	$181.80	$181.80
Purchase #6	$79.89	8.826%	$86.9411	$86.94	$86.95	$86.90
Purchase #7	$122.77	9.850%	$134.8628	$134.86	$134.85	$134.90
7 purchase totals =	$947.01		$1,028.9973	$1,029.00	$1,028.95	$1,029.00