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	$107.80	9.692%	$118.248	$118.25	$118.25	$118.20
Purchase #2	$228.84	3.831%	$237.6069	$237.61	$237.60	$237.60
Purchase #3	$164.55	4.820%	$172.4813	$172.48	$172.50	$172.50
Purchase #4	$25.43	10.392%	$28.0727	$28.07	$28.05	$28.10
Purchase #5	$80.98	12.242%	$90.8936	$90.89	$90.90	$90.90
Purchase #6	$64.45	5.673%	$68.1062	$68.11	$68.10	$68.10
Purchase #7	$50.62	4.750%	$53.0245	$53.02	$53.00	$53.00
7 purchase totals =	$722.67		$768.4332	$768.43	$768.40	$768.40