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	$31.67	13.233%	$35.8609	$35.86	$35.85	$35.90
Purchase #2	$215.43	4.808%	$225.7879	$225.79	$225.80	$225.80
Purchase #3	$110.41	11.405%	$123.0023	$123.00	$123.00	$123.00
Purchase #4	$193.42	12.595%	$217.7812	$217.78	$217.80	$217.80
Purchase #5	$142.48	11.375%	$158.6871	$158.69	$158.70	$158.70
Purchase #6	$104.79	12.578%	$117.9705	$117.97	$117.95	$118.00
Purchase #7	$40.90	10.335%	$45.127	$45.13	$45.15	$45.10
7 purchase totals =	$839.10		$924.2169	$924.22	$924.25	$924.30