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 $24.93   5.279%   $26.2461   $26.25   $26.25   $26.20  
  Purchase #2 $201.91   7.582%   $217.2188   $217.22   $217.20   $217.20  
  Purchase #3 $236.82   8.765%   $257.5773   $257.58   $257.60   $257.60  
  Purchase #4 $121.86   8.377%   $132.0682   $132.07   $132.05   $132.10  
  Purchase #5 $177.56   6.758%   $189.5595   $189.56   $189.55   $189.60  
  Purchase #6 $34.34   6.665%   $36.6288   $36.63   $36.65   $36.60  
  Purchase #7 $169.78   13.596%   $192.8633   $192.86   $192.85   $192.90  
  7 purchase totals = $967.20       $1,052.1620   $1,052.17   $1,052.15   $1,052.20