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	$126.65	3.805%	$131.469	$131.47	$131.45	$131.50
Purchase #2	$175.48	11.733%	$196.0691	$196.07	$196.05	$196.10
Purchase #3	$77.91	12.866%	$87.9339	$87.93	$87.95	$87.90
Purchase #4	$131.45	3.504%	$136.056	$136.06	$136.05	$136.10
Purchase #5	$171.51	12.304%	$192.6126	$192.61	$192.60	$192.60
Purchase #6	$86.63	13.179%	$98.047	$98.05	$98.05	$98.00
Purchase #7	$106.74	12.759%	$120.359	$120.36	$120.35	$120.40
7 purchase totals =	$876.37		$962.5466	$962.55	$962.50	$962.60