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	$192.87	9.624%	$211.4318	$211.43	$211.45	$211.40
Purchase #2	$132.58	5.254%	$139.5458	$139.55	$139.55	$139.50
Purchase #3	$23.25	7.348%	$24.9584	$24.96	$24.95	$25.00
Purchase #4	$224.72	9.264%	$245.5381	$245.54	$245.55	$245.50
Purchase #5	$158.62	11.502%	$176.8645	$176.86	$176.85	$176.90
Purchase #6	$47.31	9.561%	$51.8333	$51.83	$51.85	$51.80
Purchase #7	$178.75	10.179%	$196.945	$196.95	$196.95	$196.90
7 purchase totals =	$958.10		$1,047.1169	$1,047.12	$1,047.15	$1,047.00