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	$100.71	4.103%	$104.8421	$104.84	$104.85	$104.80
Purchase #2	$82.93	3.497%	$85.8301	$85.83	$85.85	$85.80
Purchase #3	$164.25	13.199%	$185.9294	$185.93	$185.95	$185.90
Purchase #4	$122.85	11.676%	$137.194	$137.19	$137.20	$137.20
Purchase #5	$249.56	7.794%	$269.0107	$269.01	$269.00	$269.00
Purchase #6	$45.97	12.682%	$51.7999	$51.80	$51.80	$51.80
Purchase #7	$31.47	5.167%	$33.0961	$33.10	$33.10	$33.10
7 purchase totals =	$797.74		$867.7023	$867.70	$867.75	$867.60