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 $84.27   13.446%   $95.6009   $95.60   $95.60   $95.60  
  Purchase #2 $129.27   5.167%   $135.9494   $135.95   $135.95   $135.90  
  Purchase #3 $79.91   8.352%   $86.5841   $86.58   $86.60   $86.60  
  Purchase #4 $169.44   4.776%   $177.5325   $177.53   $177.55   $177.50  
  Purchase #5 $7.31   9.598%   $8.0116   $8.01   $8.00   $8.00  
  Purchase #6 $166.43   12.189%   $186.7162   $186.72   $186.70   $186.70  
  Purchase #7 $121.64   3.336%   $125.6979   $125.70   $125.70   $125.70  
  7 purchase totals = $758.27       $816.0926   $816.09   $816.10   $816.00