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	$115.94	9.142%	$126.5392	$126.54	$126.55	$126.50
Purchase #2	$104.43	4.606%	$109.24	$109.24	$109.25	$109.20
Purchase #3	$16.53	4.850%	$17.3317	$17.33	$17.35	$17.30
Purchase #4	$32.83	7.724%	$35.3658	$35.37	$35.35	$35.40
Purchase #5	$32.54	8.852%	$35.4204	$35.42	$35.40	$35.40
Purchase #6	$162.65	12.167%	$182.4396	$182.44	$182.45	$182.40
Purchase #7	$109.35	6.572%	$116.5365	$116.54	$116.55	$116.50
7 purchase totals =	$574.27		$622.8732	$622.88	$622.90	$622.70