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	$57.51	3.864%	$59.7322	$59.73	$59.75	$59.70
Purchase #2	$135.92	5.692%	$143.6566	$143.66	$143.65	$143.70
Purchase #3	$226.97	6.404%	$241.5052	$241.51	$241.50	$241.50
Purchase #4	$114.77	7.807%	$123.7301	$123.73	$123.75	$123.70
Purchase #5	$102.51	12.704%	$115.5329	$115.53	$115.55	$115.50
Purchase #6	$141.77	7.520%	$152.4311	$152.43	$152.45	$152.40
Purchase #7	$186.77	7.850%	$201.4314	$201.43	$201.45	$201.40
7 purchase totals =	$966.22		$1,038.0195	$1,038.02	$1,038.10	$1,037.90