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 $216.72   4.867%   $227.2678   $227.27   $227.25   $227.30  
  Purchase #2 $71.95   5.664%   $76.0252   $76.03   $76.05   $76.00  
  Purchase #3 $154.56   4.791%   $161.965   $161.97   $161.95   $162.00  
  Purchase #4 $236.28   12.829%   $266.5924   $266.59   $266.60   $266.60  
  Purchase #5 $133.99   4.838%   $140.4724   $140.47   $140.45   $140.50  
  Purchase #6 $59.56   13.166%   $67.4017   $67.40   $67.40   $67.40  
  Purchase #7 $190.56   12.806%   $214.9631   $214.96   $214.95   $215.00  
  7 purchase totals = $1,063.62       $1,154.6876   $1,154.69   $1,154.65   $1,154.80