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	$184.92	4.129%	$192.5553	$192.56	$192.55	$192.60
Purchase #2	$117.57	8.138%	$127.1378	$127.14	$127.15	$127.10
Purchase #3	$226.71	6.145%	$240.6413	$240.64	$240.65	$240.60
Purchase #4	$162.90	10.273%	$179.6347	$179.63	$179.65	$179.60
Purchase #5	$81.81	8.827%	$89.0314	$89.03	$89.05	$89.00
Purchase #6	$154.83	6.468%	$164.8444	$164.84	$164.85	$164.80
Purchase #7	$250.94	6.189%	$266.4707	$266.47	$266.45	$266.50
7 purchase totals =	$1,179.68		$1,260.3156	$1,260.31	$1,260.35	$1,260.20