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	$140.99	11.686%	$157.4661	$157.47	$157.45	$157.50
Purchase #2	$104.43	13.123%	$118.1343	$118.13	$118.15	$118.10
Purchase #3	$231.26	7.439%	$248.4634	$248.46	$248.45	$248.50
Purchase #4	$198.68	8.257%	$215.085	$215.09	$215.10	$215.10
Purchase #5	$131.55	4.385%	$137.3185	$137.32	$137.30	$137.30
Purchase #6	$154.48	8.471%	$167.566	$167.57	$167.55	$167.60
Purchase #7	$124.88	13.535%	$141.7825	$141.78	$141.80	$141.80
7 purchase totals =	$1,086.27		$1,185.8158	$1,185.82	$1,185.80	$1,185.90