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	$241.73	8.409%	$262.0571	$262.06	$262.05	$262.10
Purchase #2	$120.97	13.305%	$137.0651	$137.07	$137.05	$137.10
Purchase #3	$113.74	3.657%	$117.8995	$117.90	$117.90	$117.90
Purchase #4	$136.36	6.728%	$145.5343	$145.53	$145.55	$145.50
Purchase #5	$128.43	3.146%	$132.4704	$132.47	$132.45	$132.50
Purchase #6	$70.29	11.325%	$78.2503	$78.25	$78.25	$78.30
Purchase #7	$28.61	10.485%	$31.6098	$31.61	$31.60	$31.60
7 purchase totals =	$840.13		$904.8865	$904.89	$904.85	$905.00