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	$230.80	12.765%	$260.2616	$260.26	$260.25	$260.30
Purchase #2	$166.48	3.397%	$172.1353	$172.14	$172.15	$172.10
Purchase #3	$208.62	8.293%	$225.9209	$225.92	$225.90	$225.90
Purchase #4	$114.40	12.663%	$128.8865	$128.89	$128.90	$128.90
Purchase #5	$61.69	7.808%	$66.5068	$66.51	$66.50	$66.50
Purchase #6	$74.90	13.544%	$85.0445	$85.04	$85.05	$85.00
Purchase #7	$115.82	11.348%	$128.9633	$128.96	$128.95	$129.00
7 purchase totals =	$972.71		$1,067.7189	$1,067.72	$1,067.70	$1,067.70