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	$38.25	5.558%	$40.3759	$40.38	$40.40	$40.40
Purchase #2	$86.54	3.580%	$89.6381	$89.64	$89.65	$89.60
Purchase #3	$232.52	12.529%	$261.6524	$261.65	$261.65	$261.70
Purchase #4	$169.71	13.354%	$192.3731	$192.37	$192.35	$192.40
Purchase #5	$75.62	11.833%	$84.5681	$84.57	$84.55	$84.60
Purchase #6	$191.53	7.828%	$206.523	$206.52	$206.50	$206.50
Purchase #7	$173.35	10.626%	$191.7702	$191.77	$191.75	$191.80
7 purchase totals =	$967.52		$1,066.9008	$1,066.90	$1,066.85	$1,067.00