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	$35.73	8.203%	$38.6609	$38.66	$38.65	$38.70
Purchase #2	$161.88	4.394%	$168.993	$168.99	$169.00	$169.00
Purchase #3	$82.32	3.437%	$85.1493	$85.15	$85.15	$85.10
Purchase #4	$50.98	8.106%	$55.1124	$55.11	$55.10	$55.10
Purchase #5	$47.26	10.291%	$52.1235	$52.12	$52.10	$52.10
Purchase #6	$73.91	11.463%	$82.3823	$82.38	$82.40	$82.40
Purchase #7	$229.60	11.533%	$256.0798	$256.08	$256.10	$256.10
7 purchase totals =	$681.68		$738.5012	$738.49	$738.50	$738.50