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	$140.47	8.574%	$152.5139	$152.51	$152.50	$152.50
Purchase #2	$241.75	7.360%	$259.5428	$259.54	$259.55	$259.50
Purchase #3	$193.83	11.838%	$216.7756	$216.78	$216.80	$216.80
Purchase #4	$80.69	8.463%	$87.5188	$87.52	$87.50	$87.50
Purchase #5	$183.78	4.460%	$191.9766	$191.98	$192.00	$192.00
Purchase #6	$62.47	5.739%	$66.0552	$66.06	$66.05	$66.10
Purchase #7	$151.50	10.599%	$167.5575	$167.56	$167.55	$167.60
7 purchase totals =	$1,054.49		$1,141.9404	$1,141.95	$1,141.95	$1,142.00