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 $93.76   11.572%   $104.6099   $104.61   $104.60   $104.60  
  Purchase #2 $163.56   7.461%   $175.7632   $175.76   $175.75   $175.80  
  Purchase #3 $221.46   13.275%   $250.8588   $250.86   $250.85   $250.90  
  Purchase #4 $118.53   7.396%   $127.2965   $127.30   $127.30   $127.30  
  Purchase #5 $62.69   3.845%   $65.1004   $65.10   $65.10   $65.10  
  Purchase #6 $169.63   4.577%   $177.394   $177.39   $177.40   $177.40  
  Purchase #7 $42.63   5.490%   $44.9704   $44.97   $44.95   $45.00  
  7 purchase totals = $872.26       $945.9932   $945.99   $945.95   $946.10