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	$145.67	11.487%	$162.4031	$162.40	$162.40	$162.40
Purchase #2	$202.50	11.329%	$225.4412	$225.44	$225.45	$225.40
Purchase #3	$59.39	11.545%	$66.2466	$66.25	$66.25	$66.20
Purchase #4	$38.44	5.544%	$40.5711	$40.57	$40.55	$40.60
Purchase #5	$23.78	9.233%	$25.9756	$25.98	$26.00	$26.00
Purchase #6	$63.48	4.561%	$66.3753	$66.38	$66.40	$66.40
Purchase #7	$101.85	9.807%	$111.8384	$111.84	$111.85	$111.80
7 purchase totals =	$635.11		$698.8513	$698.86	$698.90	$698.80