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	$52.90	7.584%	$56.9119	$56.91	$56.90	$56.90
Purchase #2	$5.43	10.757%	$6.0141	$6.01	$6.00	$6.00
Purchase #3	$200.32	5.302%	$210.941	$210.94	$210.95	$210.90
Purchase #4	$89.54	13.235%	$101.3906	$101.39	$101.40	$101.40
Purchase #5	$169.89	6.172%	$180.3756	$180.38	$180.40	$180.40
Purchase #6	$164.65	5.615%	$173.8951	$173.90	$173.90	$173.90
Purchase #7	$209.79	3.418%	$216.9606	$216.96	$216.95	$217.00
7 purchase totals =	$892.52		$946.4889	$946.49	$946.50	$946.50