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	$19.75	4.802%	$20.6984	$20.70	$20.70	$20.70
Purchase #2	$67.89	6.296%	$72.1644	$72.16	$72.15	$72.20
Purchase #3	$161.92	7.467%	$174.0106	$174.01	$174.00	$174.00
Purchase #4	$75.50	3.595%	$78.2142	$78.21	$78.20	$78.20
Purchase #5	$248.30	4.410%	$259.25	$259.25	$259.25	$259.30
Purchase #6	$157.86	5.749%	$166.9354	$166.94	$166.95	$166.90
Purchase #7	$123.28	9.389%	$134.8548	$134.85	$134.85	$134.90
7 purchase totals =	$854.50		$906.1278	$906.12	$906.10	$906.20