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	$96.97	8.363%	$105.0796	$105.08	$105.10	$105.10
Purchase #2	$162.39	6.257%	$172.5507	$172.55	$172.55	$172.60
Purchase #3	$70.86	5.266%	$74.5915	$74.59	$74.60	$74.60
Purchase #4	$169.62	12.548%	$190.9039	$190.90	$190.90	$190.90
Purchase #5	$177.91	9.389%	$194.614	$194.61	$194.60	$194.60
Purchase #6	$164.76	6.717%	$175.8269	$175.83	$175.85	$175.80
Purchase #7	$119.60	3.102%	$123.31	$123.31	$123.30	$123.30
7 purchase totals =	$962.11		$1,036.8766	$1,036.87	$1,036.90	$1,036.90