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	$202.48	13.628%	$230.074	$230.07	$230.05	$230.10
Purchase #2	$121.75	8.275%	$131.8248	$131.82	$131.80	$131.80
Purchase #3	$47.59	8.331%	$51.5547	$51.55	$51.55	$51.60
Purchase #4	$9.94	11.189%	$11.0522	$11.05	$11.05	$11.10
Purchase #5	$143.70	6.274%	$152.7157	$152.72	$152.70	$152.70
Purchase #6	$78.45	9.412%	$85.8337	$85.83	$85.85	$85.80
Purchase #7	$213.66	4.798%	$223.9114	$223.91	$223.90	$223.90
7 purchase totals =	$817.57		$886.9665	$886.95	$886.90	$887.00