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	$71.80	9.485%	$78.6102	$78.61	$78.60	$78.60
Purchase #2	$31.29	6.271%	$33.2522	$33.25	$33.25	$33.30
Purchase #3	$180.32	3.622%	$186.8512	$186.85	$186.85	$186.90
Purchase #4	$109.63	13.787%	$124.7447	$124.74	$124.75	$124.70
Purchase #5	$46.57	11.509%	$51.9297	$51.93	$51.95	$51.90
Purchase #6	$83.52	13.615%	$94.8912	$94.89	$94.90	$94.90
Purchase #7	$81.68	5.649%	$86.2941	$86.29	$86.30	$86.30
7 purchase totals =	$604.81		$656.5733	$656.56	$656.60	$656.60