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	$246.86	10.540%	$272.879	$272.88	$272.90	$272.90
Purchase #2	$156.52	4.523%	$163.5994	$163.60	$163.60	$163.60
Purchase #3	$51.44	6.655%	$54.8633	$54.86	$54.85	$54.90
Purchase #4	$138.59	8.512%	$150.3868	$150.39	$150.40	$150.40
Purchase #5	$114.98	7.167%	$123.2206	$123.22	$123.20	$123.20
Purchase #6	$72.38	6.148%	$76.8299	$76.83	$76.85	$76.80
Purchase #7	$240.89	11.704%	$269.0838	$269.08	$269.10	$269.10
7 purchase totals =	$1,021.66		$1,110.8628	$1,110.86	$1,110.90	$1,110.90