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	$233.55	3.284%	$241.2198	$241.22	$241.20	$241.20
Purchase #2	$72.29	13.300%	$81.9046	$81.90	$81.90	$81.90
Purchase #3	$168.60	4.440%	$176.0858	$176.09	$176.10	$176.10
Purchase #4	$40.91	12.126%	$45.8707	$45.87	$45.85	$45.90
Purchase #5	$212.43	12.191%	$238.3273	$238.33	$238.35	$238.30
Purchase #6	$217.73	9.267%	$237.907	$237.91	$237.90	$237.90
Purchase #7	$80.62	7.312%	$86.5149	$86.51	$86.50	$86.50
7 purchase totals =	$1,026.13		$1,107.8301	$1,107.83	$1,107.80	$1,107.80