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	$170.29	6.794%	$181.8595	$181.86	$181.85	$181.90
Purchase #2	$180.78	5.391%	$190.5258	$190.53	$190.55	$190.50
Purchase #3	$107.50	3.329%	$111.0787	$111.08	$111.10	$111.10
Purchase #4	$113.73	3.726%	$117.9676	$117.97	$117.95	$118.00
Purchase #5	$145.29	13.248%	$164.538	$164.54	$164.55	$164.50
Purchase #6	$81.31	4.209%	$84.7323	$84.73	$84.75	$84.70
Purchase #7	$236.54	9.847%	$259.8321	$259.83	$259.85	$259.80
7 purchase totals =	$1,035.44		$1,110.5340	$1,110.54	$1,110.60	$1,110.50