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	$14.61	11.119%	$16.2345	$16.23	$16.25	$16.20
Purchase #2	$78.74	4.727%	$82.462	$82.46	$82.45	$82.50
Purchase #3	$156.52	7.365%	$168.0477	$168.05	$168.05	$168.00
Purchase #4	$98.44	13.419%	$111.6497	$111.65	$111.65	$111.60
Purchase #5	$44.52	4.426%	$46.4905	$46.49	$46.50	$46.50
Purchase #6	$214.44	12.686%	$241.6439	$241.64	$241.65	$241.60
Purchase #7	$190.93	4.121%	$198.7982	$198.80	$198.80	$198.80
7 purchase totals =	$798.20		$865.3265	$865.32	$865.35	$865.20