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	$105.45	10.160%	$116.1637	$116.16	$116.15	$116.20
Purchase #2	$78.78	8.345%	$85.3542	$85.35	$85.35	$85.40
Purchase #3	$137.93	12.739%	$155.5009	$155.50	$155.50	$155.50
Purchase #4	$245.54	13.605%	$278.9457	$278.95	$278.95	$278.90
Purchase #5	$181.76	9.360%	$198.7727	$198.77	$198.75	$198.80
Purchase #6	$185.73	13.156%	$210.1646	$210.16	$210.15	$210.20
Purchase #7	$194.85	9.809%	$213.9628	$213.96	$213.95	$214.00
7 purchase totals =	$1,130.04		$1,258.8646	$1,258.85	$1,258.80	$1,259.00