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	$57.29	9.271%	$62.6014	$62.60	$62.60	$62.60
Purchase #2	$122.97	11.744%	$137.4116	$137.41	$137.40	$137.40
Purchase #3	$28.36	12.269%	$31.8395	$31.84	$31.85	$31.80
Purchase #4	$8.60	3.451%	$8.8968	$8.90	$8.90	$8.90
Purchase #5	$145.89	12.732%	$164.4647	$164.46	$164.45	$164.50
Purchase #6	$161.59	13.440%	$183.3077	$183.31	$183.30	$183.30
Purchase #7	$161.59	11.327%	$179.8933	$179.89	$179.90	$179.90
7 purchase totals =	$686.29		$768.4150	$768.41	$768.40	$768.40