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	$13.26	5.156%	$13.9437	$13.94	$13.95	$13.90
Purchase #2	$100.48	11.678%	$112.2141	$112.21	$112.20	$112.20
Purchase #3	$41.42	10.162%	$45.6291	$45.63	$45.65	$45.60
Purchase #4	$59.69	4.454%	$62.3486	$62.35	$62.35	$62.30
Purchase #5	$40.62	8.582%	$44.106	$44.11	$44.10	$44.10
Purchase #6	$100.47	9.319%	$109.8328	$109.83	$109.85	$109.80
Purchase #7	$195.57	6.586%	$208.4502	$208.45	$208.45	$208.50
7 purchase totals =	$551.51		$596.5245	$596.52	$596.55	$596.40