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	$201.83	10.752%	$223.5308	$223.53	$223.55	$223.50
Purchase #2	$200.26	13.299%	$226.8926	$226.89	$226.90	$226.90
Purchase #3	$104.69	10.353%	$115.5286	$115.53	$115.55	$115.50
Purchase #4	$86.50	11.185%	$96.175	$96.18	$96.20	$96.20
Purchase #5	$50.81	4.159%	$52.9232	$52.92	$52.90	$52.90
Purchase #6	$250.48	9.235%	$273.6118	$273.61	$273.60	$273.60
Purchase #7	$10.71	10.675%	$11.8533	$11.85	$11.85	$11.90
7 purchase totals =	$905.28		$1,000.5153	$1,000.51	$1,000.55	$1,000.50