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	$202.35	11.497%	$225.6142	$225.61	$225.60	$225.60
Purchase #2	$43.81	3.854%	$45.4984	$45.50	$45.50	$45.50
Purchase #3	$174.93	9.541%	$191.6201	$191.62	$191.60	$191.60
Purchase #4	$215.50	4.561%	$225.329	$225.33	$225.35	$225.30
Purchase #5	$103.98	3.271%	$107.3812	$107.38	$107.40	$107.40
Purchase #6	$81.49	6.552%	$86.8292	$86.83	$86.85	$86.80
Purchase #7	$187.47	9.730%	$205.7108	$205.71	$205.70	$205.70
7 purchase totals =	$1,009.53		$1,087.9829	$1,087.98	$1,088.00	$1,087.90