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 $54.44   7.601%   $58.578   $58.58   $58.60   $58.60  
  Purchase #2 $84.82   8.768%   $92.257   $92.26   $92.25   $92.30  
  Purchase #3 $197.85   4.602%   $206.9551   $206.96   $206.95   $207.00  
  Purchase #4 $246.65   6.163%   $261.851   $261.85   $261.85   $261.90  
  Purchase #5 $237.63   4.113%   $247.4037   $247.40   $247.40   $247.40  
  Purchase #6 $55.82   3.682%   $57.8753   $57.88   $57.90   $57.90  
  Purchase #7 $120.30   6.342%   $127.9294   $127.93   $127.95   $127.90  
  7 purchase totals = $997.51       $1,052.8495   $1,052.86   $1,052.90   $1,053.00