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	$131.73	11.493%	$146.8697	$146.87	$146.85	$146.90
Purchase #2	$39.46	3.671%	$40.9086	$40.91	$40.90	$40.90
Purchase #3	$177.51	8.600%	$192.7759	$192.78	$192.80	$192.80
Purchase #4	$192.37	6.570%	$205.0087	$205.01	$205.00	$205.00
Purchase #5	$188.83	8.271%	$204.4481	$204.45	$204.45	$204.40
Purchase #6	$87.53	7.493%	$94.0886	$94.09	$94.10	$94.10
Purchase #7	$127.70	10.771%	$141.4546	$141.45	$141.45	$141.50
7 purchase totals =	$945.13		$1,025.5542	$1,025.56	$1,025.55	$1,025.60