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	$19.49	13.418%	$22.1052	$22.11	$22.10	$22.10
Purchase #2	$159.82	4.168%	$166.4813	$166.48	$166.50	$166.50
Purchase #3	$242.82	6.697%	$259.0817	$259.08	$259.10	$259.10
Purchase #4	$215.84	13.555%	$245.0971	$245.10	$245.10	$245.10
Purchase #5	$88.93	7.363%	$95.4779	$95.48	$95.50	$95.50
Purchase #6	$96.45	9.490%	$105.6031	$105.60	$105.60	$105.60
Purchase #7	$208.35	3.662%	$215.9798	$215.98	$216.00	$216.00
7 purchase totals =	$1,031.70		$1,109.8261	$1,109.83	$1,109.90	$1,109.90