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	$95.93	4.457%	$100.2056	$100.21	$100.20	$100.20
Purchase #2	$62.31	8.360%	$67.5191	$67.52	$67.50	$67.50
Purchase #3	$73.89	4.105%	$76.9232	$76.92	$76.90	$76.90
Purchase #4	$243.97	9.671%	$267.5643	$267.56	$267.55	$267.60
Purchase #5	$250.49	11.527%	$279.364	$279.36	$279.35	$279.40
Purchase #6	$127.73	4.574%	$133.5724	$133.57	$133.55	$133.60
Purchase #7	$120.49	11.226%	$134.0162	$134.02	$134.00	$134.00
7 purchase totals =	$974.81		$1,059.1648	$1,059.16	$1,059.05	$1,059.20