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	$226.36	6.443%	$240.9444	$240.94	$240.95	$240.90
Purchase #2	$191.40	11.244%	$212.921	$212.92	$212.90	$212.90
Purchase #3	$182.98	13.617%	$207.8964	$207.90	$207.90	$207.90
Purchase #4	$129.96	11.273%	$144.6104	$144.61	$144.60	$144.60
Purchase #5	$80.48	12.782%	$90.767	$90.77	$90.75	$90.80
Purchase #6	$166.99	10.695%	$184.8496	$184.85	$184.85	$184.80
Purchase #7	$24.77	11.527%	$27.6252	$27.63	$27.65	$27.60
7 purchase totals =	$1,002.94		$1,109.6140	$1,109.62	$1,109.60	$1,109.50