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	$106.70	7.379%	$114.5734	$114.57	$114.55	$114.60
Purchase #2	$201.83	3.319%	$208.5287	$208.53	$208.55	$208.50
Purchase #3	$115.44	4.244%	$120.3393	$120.34	$120.35	$120.30
Purchase #4	$116.75	9.289%	$127.5949	$127.59	$127.60	$127.60
Purchase #5	$106.66	7.552%	$114.715	$114.72	$114.70	$114.70
Purchase #6	$176.83	4.677%	$185.1003	$185.10	$185.10	$185.10
Purchase #7	$46.56	13.167%	$52.6906	$52.69	$52.70	$52.70
7 purchase totals =	$870.77		$923.5422	$923.54	$923.55	$923.50