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	$116.60	9.691%	$127.8997	$127.90	$127.90	$127.90
Purchase #2	$131.25	6.319%	$139.5437	$139.54	$139.55	$139.50
Purchase #3	$232.70	9.643%	$255.1393	$255.14	$255.15	$255.10
Purchase #4	$128.37	7.202%	$137.6152	$137.62	$137.60	$137.60
Purchase #5	$12.76	11.652%	$14.2468	$14.25	$14.25	$14.20
Purchase #6	$228.39	10.128%	$251.5213	$251.52	$251.50	$251.50
Purchase #7	$97.48	5.506%	$102.8472	$102.85	$102.85	$102.80
7 purchase totals =	$947.55		$1,028.8132	$1,028.82	$1,028.80	$1,028.60