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	$58.65	11.540%	$65.4182	$65.42	$65.40	$65.40
Purchase #2	$236.33	5.500%	$249.3282	$249.33	$249.35	$249.30
Purchase #3	$204.98	8.752%	$222.9198	$222.92	$222.90	$222.90
Purchase #4	$107.43	6.158%	$114.0455	$114.05	$114.05	$114.00
Purchase #5	$118.93	10.243%	$131.112	$131.11	$131.10	$131.10
Purchase #6	$200.96	8.578%	$218.1983	$218.20	$218.20	$218.20
Purchase #7	$187.83	4.137%	$195.6005	$195.60	$195.60	$195.60
7 purchase totals =	$1,115.11		$1,196.6225	$1,196.63	$1,196.60	$1,196.50