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	$65.80	5.751%	$69.5842	$69.58	$69.60	$69.60
Purchase #2	$96.83	13.379%	$109.7849	$109.78	$109.80	$109.80
Purchase #3	$31.25	12.359%	$35.1122	$35.11	$35.10	$35.10
Purchase #4	$235.69	6.466%	$250.9297	$250.93	$250.95	$250.90
Purchase #5	$147.46	9.277%	$161.1399	$161.14	$161.15	$161.10
Purchase #6	$78.84	10.359%	$87.007	$87.01	$87.00	$87.00
Purchase #7	$40.60	5.647%	$42.8927	$42.89	$42.90	$42.90
7 purchase totals =	$696.47		$756.4506	$756.44	$756.50	$756.40