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	$194.86	7.830%	$210.1175	$210.12	$210.10	$210.10
Purchase #2	$133.62	5.864%	$141.4555	$141.46	$141.45	$141.50
Purchase #3	$47.87	9.579%	$52.4555	$52.46	$52.45	$52.50
Purchase #4	$226.64	10.271%	$249.9182	$249.92	$249.90	$249.90
Purchase #5	$153.78	12.238%	$172.5996	$172.60	$172.60	$172.60
Purchase #6	$36.93	13.736%	$42.0027	$42.00	$42.00	$42.00
Purchase #7	$164.96	7.553%	$177.4194	$177.42	$177.40	$177.40
7 purchase totals =	$958.66		$1,045.9684	$1,045.98	$1,045.90	$1,046.00