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 $104.61   8.676%   $113.686   $113.69   $113.70   $113.70  
  Purchase #2 $192.65   6.262%   $204.7137   $204.71   $204.70   $204.70  
  Purchase #3 $224.72   5.261%   $236.5425   $236.54   $236.55   $236.50  
  Purchase #4 $227.29   6.336%   $241.6911   $241.69   $241.70   $241.70  
  Purchase #5 $249.97   9.618%   $274.0121   $274.01   $274.00   $274.00  
  Purchase #6 $172.98   6.387%   $184.0282   $184.03   $184.05   $184.00  
  Purchase #7 $84.83   8.513%   $92.0516   $92.05   $92.05   $92.10  
  7 purchase totals = $1,257.05       $1,346.7252   $1,346.72   $1,346.75   $1,346.70