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 $55.86   10.750%   $61.865   $61.87   $61.85   $61.90  
  Purchase #2 $246.72   13.438%   $279.8742   $279.87   $279.85   $279.90  
  Purchase #3 $249.99   4.825%   $262.052   $262.05   $262.05   $262.10  
  Purchase #4 $103.35   7.150%   $110.7395   $110.74   $110.75   $110.70  
  Purchase #5 $105.47   3.779%   $109.4557   $109.46   $109.45   $109.50  
  Purchase #6 $53.69   8.374%   $58.186   $58.19   $58.20   $58.20  
  Purchase #7 $76.84   7.289%   $82.4409   $82.44   $82.45   $82.40  
  7 purchase totals = $891.92       $964.6133   $964.62   $964.60   $964.70