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 $35.48   4.838%   $37.1965   $37.20   $37.20   $37.20  
  Purchase #2 $225.78   11.189%   $251.0425   $251.04   $251.05   $251.00  
  Purchase #3 $160.57   11.839%   $179.5799   $179.58   $179.60   $179.60  
  Purchase #4 $51.57   6.575%   $54.9607   $54.96   $54.95   $55.00  
  Purchase #5 $28.92   4.834%   $30.318   $30.32   $30.30   $30.30  
  Purchase #6 $204.84   4.754%   $214.5781   $214.58   $214.60   $214.60  
  Purchase #7 $237.53   7.348%   $254.9837   $254.98   $255.00   $255.00  
  7 purchase totals = $944.69       $1,022.6594   $1,022.66   $1,022.70   $1,022.70