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	$143.84	9.260%	$157.1596	$157.16	$157.15	$157.20
Purchase #2	$227.88	6.142%	$241.8764	$241.88	$241.90	$241.90
Purchase #3	$131.31	11.238%	$146.0666	$146.07	$146.05	$146.10
Purchase #4	$157.34	3.407%	$162.7006	$162.70	$162.70	$162.70
Purchase #5	$78.92	13.344%	$89.4511	$89.45	$89.45	$89.50
Purchase #6	$204.94	8.436%	$222.2287	$222.23	$222.25	$222.20
Purchase #7	$114.53	6.272%	$121.7133	$121.71	$121.70	$121.70
7 purchase totals =	$1,058.76		$1,141.1963	$1,141.20	$1,141.20	$1,141.30