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	$83.46	5.296%	$87.88	$87.88	$87.90	$87.90
Purchase #2	$168.26	6.683%	$179.5048	$179.50	$179.50	$179.50
Purchase #3	$52.56	8.804%	$57.1874	$57.19	$57.20	$57.20
Purchase #4	$217.96	12.353%	$244.8846	$244.88	$244.90	$244.90
Purchase #5	$70.54	10.493%	$77.9418	$77.94	$77.95	$77.90
Purchase #6	$181.45	5.690%	$191.7745	$191.77	$191.75	$191.80
Purchase #7	$161.85	11.691%	$180.7719	$180.77	$180.75	$180.80
7 purchase totals =	$936.08		$1,019.9450	$1,019.93	$1,019.95	$1,020.00