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	$245.90	6.733%	$262.4564	$262.46	$262.45	$262.50
Purchase #2	$46.25	9.326%	$50.5633	$50.56	$50.55	$50.60
Purchase #3	$123.61	12.647%	$139.243	$139.24	$139.25	$139.20
Purchase #4	$44.58	12.508%	$50.1561	$50.16	$50.15	$50.20
Purchase #5	$114.42	8.309%	$123.9272	$123.93	$123.95	$123.90
Purchase #6	$172.25	5.661%	$182.0011	$182.00	$182.00	$182.00
Purchase #7	$122.89	3.462%	$127.1445	$127.14	$127.15	$127.10
7 purchase totals =	$869.90		$935.4916	$935.49	$935.50	$935.50