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	$231.78	4.314%	$241.779	$241.78	$241.80	$241.80
Purchase #2	$99.53	13.708%	$113.1736	$113.17	$113.15	$113.20
Purchase #3	$36.45	5.473%	$38.4449	$38.44	$38.45	$38.40
Purchase #4	$198.49	5.513%	$209.4328	$209.43	$209.45	$209.40
Purchase #5	$131.47	7.390%	$141.1856	$141.19	$141.20	$141.20
Purchase #6	$166.47	3.651%	$172.5478	$172.55	$172.55	$172.50
Purchase #7	$71.82	3.807%	$74.5542	$74.55	$74.55	$74.60
7 purchase totals =	$936.01		$991.1179	$991.11	$991.15	$991.10