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	$239.51	9.161%	$261.4515	$261.45	$261.45	$261.50
Purchase #2	$16.59	6.271%	$17.6304	$17.63	$17.65	$17.60
Purchase #3	$133.77	4.583%	$139.9007	$139.90	$139.90	$139.90
Purchase #4	$83.60	8.476%	$90.6859	$90.69	$90.70	$90.70
Purchase #5	$197.97	8.818%	$215.427	$215.43	$215.45	$215.40
Purchase #6	$110.57	11.473%	$123.2557	$123.26	$123.25	$123.30
Purchase #7	$145.85	8.408%	$158.1131	$158.11	$158.10	$158.10
7 purchase totals =	$927.86		$1,006.4643	$1,006.47	$1,006.50	$1,006.50