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	$107.88	3.601%	$111.7648	$111.76	$111.75	$111.80
Purchase #2	$241.82	7.856%	$260.8174	$260.82	$260.80	$260.80
Purchase #3	$114.97	4.224%	$119.8263	$119.83	$119.85	$119.80
Purchase #4	$170.63	9.159%	$186.258	$186.26	$186.25	$186.30
Purchase #5	$59.95	12.520%	$67.4557	$67.46	$67.45	$67.50
Purchase #6	$42.95	7.352%	$46.1077	$46.11	$46.10	$46.10
Purchase #7	$205.63	6.746%	$219.5018	$219.50	$219.50	$219.50
7 purchase totals =	$943.83		$1,011.7317	$1,011.74	$1,011.70	$1,011.80