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	$126.74	8.528%	$137.5484	$137.55	$137.55	$137.50
Purchase #2	$165.31	12.729%	$186.3523	$186.35	$186.35	$186.40
Purchase #3	$86.53	4.743%	$90.6341	$90.63	$90.65	$90.60
Purchase #4	$207.59	10.765%	$229.9371	$229.94	$229.95	$229.90
Purchase #5	$163.49	13.362%	$185.3355	$185.34	$185.35	$185.30
Purchase #6	$120.78	9.296%	$132.0077	$132.01	$132.00	$132.00
Purchase #7	$198.85	11.780%	$222.2745	$222.27	$222.25	$222.30
7 purchase totals =	$1,069.29		$1,184.0896	$1,184.09	$1,184.10	$1,184.00