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	$214.97	5.406%	$226.5913	$226.59	$226.60	$226.60
Purchase #2	$35.33	13.438%	$40.0776	$40.08	$40.10	$40.10
Purchase #3	$116.78	13.322%	$132.3374	$132.34	$132.35	$132.30
Purchase #4	$218.77	13.778%	$248.9121	$248.91	$248.90	$248.90
Purchase #5	$69.30	3.742%	$71.8932	$71.89	$71.90	$71.90
Purchase #6	$95.25	9.252%	$104.0625	$104.06	$104.05	$104.10
Purchase #7	$208.83	6.398%	$222.1909	$222.19	$222.20	$222.20
7 purchase totals =	$959.23		$1,046.0650	$1,046.06	$1,046.10	$1,046.10