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	$56.45	10.675%	$62.476	$62.48	$62.50	$62.50
Purchase #2	$249.89	7.124%	$267.6922	$267.69	$267.70	$267.70
Purchase #3	$123.64	3.227%	$127.6299	$127.63	$127.65	$127.60
Purchase #4	$126.73	13.546%	$143.8968	$143.90	$143.90	$143.90
Purchase #5	$148.80	4.508%	$155.5079	$155.51	$155.50	$155.50
Purchase #6	$30.38	12.148%	$34.0706	$34.07	$34.05	$34.10
Purchase #7	$179.48	12.328%	$201.6063	$201.61	$201.60	$201.60
7 purchase totals =	$915.37		$992.8797	$992.89	$992.90	$992.90