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	$55.29	12.675%	$62.298	$62.30	$62.30	$62.30
Purchase #2	$11.61	3.334%	$11.9971	$12.00	$12.00	$12.00
Purchase #3	$67.31	9.834%	$73.9293	$73.93	$73.95	$73.90
Purchase #4	$100.77	7.722%	$108.5515	$108.55	$108.55	$108.60
Purchase #5	$174.48	3.122%	$179.9273	$179.93	$179.95	$179.90
Purchase #6	$127.82	12.590%	$143.9125	$143.91	$143.90	$143.90
Purchase #7	$47.42	8.503%	$51.4521	$51.45	$51.45	$51.50
7 purchase totals =	$584.70		$632.0678	$632.07	$632.10	$632.10