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 $60.88   4.202%   $63.4382   $63.44   $63.45   $63.40  
  Purchase #2 $159.89   4.238%   $166.6661   $166.67   $166.65   $166.70  
  Purchase #3 $241.44   8.618%   $262.2473   $262.25   $262.25   $262.20  
  Purchase #4 $215.85   13.219%   $244.3832   $244.38   $244.40   $244.40  
  Purchase #5 $125.50   5.644%   $132.5832   $132.58   $132.60   $132.60  
  Purchase #6 $180.51   8.181%   $195.2775   $195.28   $195.30   $195.30  
  Purchase #7 $217.70   8.660%   $236.5528   $236.55   $236.55   $236.60  
  7 purchase totals = $1,201.77       $1,301.1483   $1,301.15   $1,301.20   $1,301.20