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	$127.86	3.108%	$131.8339	$131.83	$131.85	$131.80
Purchase #2	$10.41	12.751%	$11.7374	$11.74	$11.75	$11.70
Purchase #3	$38.49	13.309%	$43.6126	$43.61	$43.60	$43.60
Purchase #4	$176.71	3.127%	$182.2357	$182.24	$182.25	$182.20
Purchase #5	$145.79	13.145%	$164.9541	$164.95	$164.95	$165.00
Purchase #6	$241.78	3.231%	$249.5919	$249.59	$249.60	$249.60
Purchase #7	$180.79	10.214%	$199.2559	$199.26	$199.25	$199.30
7 purchase totals =	$921.83		$983.2215	$983.22	$983.25	$983.20