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	$104.57	7.507%	$112.4201	$112.42	$112.40	$112.40
Purchase #2	$45.79	4.698%	$47.9412	$47.94	$47.95	$47.90
Purchase #3	$167.52	12.480%	$188.4265	$188.43	$188.45	$188.40
Purchase #4	$237.32	8.345%	$257.1244	$257.12	$257.10	$257.10
Purchase #5	$171.78	13.202%	$194.4584	$194.46	$194.45	$194.50
Purchase #6	$224.27	3.249%	$231.5565	$231.56	$231.55	$231.60
Purchase #7	$41.69	4.393%	$43.5214	$43.52	$43.50	$43.50
7 purchase totals =	$992.94		$1,075.4485	$1,075.45	$1,075.40	$1,075.40