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	$181.69	10.273%	$200.355	$200.36	$200.35	$200.40
Purchase #2	$41.79	13.328%	$47.3598	$47.36	$47.35	$47.40
Purchase #3	$160.38	7.511%	$172.4261	$172.43	$172.45	$172.40
Purchase #4	$119.35	4.632%	$124.8783	$124.88	$124.90	$124.90
Purchase #5	$181.25	9.339%	$198.1769	$198.18	$198.20	$198.20
Purchase #6	$97.54	3.833%	$101.2787	$101.28	$101.30	$101.30
Purchase #7	$14.89	4.795%	$15.604	$15.60	$15.60	$15.60
7 purchase totals =	$796.89		$860.0788	$860.09	$860.15	$860.20