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	$49.47	12.304%	$55.5568	$55.56	$55.55	$55.60
Purchase #2	$13.38	12.819%	$15.0952	$15.10	$15.10	$15.10
Purchase #3	$198.71	6.635%	$211.8944	$211.89	$211.90	$211.90
Purchase #4	$188.92	4.324%	$197.0889	$197.09	$197.10	$197.10
Purchase #5	$78.69	5.354%	$82.9031	$82.90	$82.90	$82.90
Purchase #6	$210.81	3.386%	$217.948	$217.95	$217.95	$217.90
Purchase #7	$205.46	12.622%	$231.3932	$231.39	$231.40	$231.40
7 purchase totals =	$945.44		$1,011.8796	$1,011.88	$1,011.90	$1,011.90