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	$86.41	10.301%	$95.3111	$95.31	$95.30	$95.30
Purchase #2	$183.51	8.386%	$198.8991	$198.90	$198.90	$198.90
Purchase #3	$27.49	7.800%	$29.6342	$29.63	$29.65	$29.60
Purchase #4	$164.83	12.158%	$184.87	$184.87	$184.85	$184.90
Purchase #5	$188.80	3.859%	$196.0858	$196.09	$196.10	$196.10
Purchase #6	$210.85	7.779%	$227.252	$227.25	$227.25	$227.30
Purchase #7	$218.47	12.550%	$245.888	$245.89	$245.90	$245.90
7 purchase totals =	$1,080.36		$1,177.9402	$1,177.94	$1,177.95	$1,178.00