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	$165.57	9.249%	$180.8836	$180.88	$180.90	$180.90
Purchase #2	$166.46	8.709%	$180.957	$180.96	$180.95	$181.00
Purchase #3	$41.75	3.218%	$43.0935	$43.09	$43.10	$43.10
Purchase #4	$87.88	13.843%	$100.0452	$100.05	$100.05	$100.00
Purchase #5	$43.37	9.328%	$47.4156	$47.42	$47.40	$47.40
Purchase #6	$137.35	4.619%	$143.6942	$143.69	$143.70	$143.70
Purchase #7	$146.94	13.678%	$167.0385	$167.04	$167.05	$167.00
7 purchase totals =	$789.32		$863.1276	$863.13	$863.15	$863.10