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	$12.33	13.216%	$13.9595	$13.96	$13.95	$14.00
Purchase #2	$143.78	6.815%	$153.5786	$153.58	$153.60	$153.60
Purchase #3	$115.69	6.733%	$123.4794	$123.48	$123.50	$123.50
Purchase #4	$109.55	10.217%	$120.7427	$120.74	$120.75	$120.70
Purchase #5	$110.36	11.541%	$123.0966	$123.10	$123.10	$123.10
Purchase #6	$223.48	7.429%	$240.0823	$240.08	$240.10	$240.10
Purchase #7	$224.58	6.161%	$238.4164	$238.42	$238.40	$238.40
7 purchase totals =	$939.77		$1,013.3555	$1,013.36	$1,013.40	$1,013.40