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	$131.52	8.293%	$142.427	$142.43	$142.45	$142.40
Purchase #2	$165.89	12.409%	$186.4753	$186.48	$186.50	$186.50
Purchase #3	$217.78	8.628%	$236.5701	$236.57	$236.55	$236.60
Purchase #4	$73.81	13.190%	$83.5455	$83.55	$83.55	$83.50
Purchase #5	$31.68	12.712%	$35.7072	$35.71	$35.70	$35.70
Purchase #6	$60.86	10.484%	$67.2406	$67.24	$67.25	$67.20
Purchase #7	$231.44	12.753%	$260.9555	$260.96	$260.95	$261.00
7 purchase totals =	$912.98		$1,012.9212	$1,012.94	$1,012.95	$1,012.90