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	$161.95	7.405%	$173.9424	$173.94	$173.95	$173.90
Purchase #2	$107.70	9.507%	$117.939	$117.94	$117.95	$117.90
Purchase #3	$107.38	4.637%	$112.3592	$112.36	$112.35	$112.40
Purchase #4	$168.90	12.851%	$190.6053	$190.61	$190.60	$190.60
Purchase #5	$40.74	5.292%	$42.896	$42.90	$42.90	$42.90
Purchase #6	$186.47	5.426%	$196.5879	$196.59	$196.60	$196.60
Purchase #7	$78.45	13.374%	$88.9419	$88.94	$88.95	$88.90
7 purchase totals =	$851.59		$923.2717	$923.28	$923.30	$923.20