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	$37.34	4.257%	$38.9296	$38.93	$38.95	$38.90
Purchase #2	$76.67	9.765%	$84.1568	$84.16	$84.15	$84.20
Purchase #3	$102.52	10.681%	$113.4702	$113.47	$113.45	$113.50
Purchase #4	$243.48	5.455%	$256.7618	$256.76	$256.75	$256.80
Purchase #5	$75.80	9.412%	$82.9343	$82.93	$82.95	$82.90
Purchase #6	$78.75	13.617%	$89.4734	$89.47	$89.45	$89.50
Purchase #7	$17.71	4.386%	$18.4868	$18.49	$18.50	$18.50
7 purchase totals =	$632.27		$684.2129	$684.21	$684.20	$684.30