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	$239.34	7.337%	$256.9004	$256.90	$256.90	$256.90
Purchase #2	$34.90	5.622%	$36.8621	$36.86	$36.85	$36.90
Purchase #3	$157.86	11.558%	$176.1055	$176.11	$176.10	$176.10
Purchase #4	$80.32	6.591%	$85.6139	$85.61	$85.60	$85.60
Purchase #5	$80.47	3.270%	$83.1014	$83.10	$83.10	$83.10
Purchase #6	$185.97	8.371%	$201.5375	$201.54	$201.55	$201.50
Purchase #7	$142.93	13.625%	$162.4042	$162.40	$162.40	$162.40
7 purchase totals =	$921.79		$1,002.5250	$1,002.52	$1,002.50	$1,002.50