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	$216.28	13.189%	$244.8052	$244.81	$244.80	$244.80
Purchase #2	$145.60	9.802%	$159.8717	$159.87	$159.85	$159.90
Purchase #3	$56.93	4.677%	$59.5926	$59.59	$59.60	$59.60
Purchase #4	$228.67	10.590%	$252.8862	$252.89	$252.90	$252.90
Purchase #5	$168.78	10.756%	$186.934	$186.93	$186.95	$186.90
Purchase #6	$38.54	12.408%	$43.322	$43.32	$43.30	$43.30
Purchase #7	$39.53	12.645%	$44.5286	$44.53	$44.55	$44.50
7 purchase totals =	$894.33		$991.9403	$991.94	$991.95	$991.90