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	$248.94	5.233%	$261.967	$261.97	$261.95	$262.00
Purchase #2	$240.98	3.831%	$250.2119	$250.21	$250.20	$250.20
Purchase #3	$110.53	3.733%	$114.6561	$114.66	$114.65	$114.70
Purchase #4	$54.82	10.703%	$60.6874	$60.69	$60.70	$60.70
Purchase #5	$121.45	5.155%	$127.7107	$127.71	$127.70	$127.70
Purchase #6	$76.78	12.634%	$86.4804	$86.48	$86.50	$86.50
Purchase #7	$181.41	8.552%	$196.9242	$196.92	$196.90	$196.90
7 purchase totals =	$1,034.91		$1,098.6377	$1,098.64	$1,098.60	$1,098.70