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	$104.42	6.682%	$111.3973	$111.40	$111.40	$111.40
Purchase #2	$187.68	6.791%	$200.4253	$200.43	$200.45	$200.40
Purchase #3	$233.43	6.193%	$247.8863	$247.89	$247.90	$247.90
Purchase #4	$59.42	10.697%	$65.7762	$65.78	$65.80	$65.80
Purchase #5	$179.79	3.738%	$186.5106	$186.51	$186.50	$186.50
Purchase #6	$207.58	3.398%	$214.6336	$214.63	$214.65	$214.60
Purchase #7	$107.59	8.803%	$117.0611	$117.06	$117.05	$117.10
7 purchase totals =	$1,079.91		$1,143.6904	$1,143.70	$1,143.75	$1,143.70