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	$31.25	13.308%	$35.4088	$35.41	$35.40	$35.40
Purchase #2	$229.53	5.411%	$241.9499	$241.95	$241.95	$241.90
Purchase #3	$156.90	11.868%	$175.5209	$175.52	$175.50	$175.50
Purchase #4	$143.72	8.142%	$155.4217	$155.42	$155.40	$155.40
Purchase #5	$203.46	12.136%	$228.1519	$228.15	$228.15	$228.20
Purchase #6	$13.26	5.438%	$13.9811	$13.98	$14.00	$14.00
Purchase #7	$155.66	4.649%	$162.8966	$162.90	$162.90	$162.90
7 purchase totals =	$933.78		$1,013.3309	$1,013.33	$1,013.30	$1,013.30