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	$150.79	3.179%	$155.5836	$155.58	$155.60	$155.60
Purchase #2	$154.90	8.198%	$167.5987	$167.60	$167.60	$167.60
Purchase #3	$152.94	5.544%	$161.419	$161.42	$161.40	$161.40
Purchase #4	$192.69	11.562%	$214.9688	$214.97	$214.95	$215.00
Purchase #5	$46.71	12.571%	$52.5819	$52.58	$52.60	$52.60
Purchase #6	$244.53	12.304%	$274.617	$274.62	$274.60	$274.60
Purchase #7	$176.31	11.220%	$196.092	$196.09	$196.10	$196.10
7 purchase totals =	$1,118.87		$1,222.8610	$1,222.86	$1,222.85	$1,222.90