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 $182.68   10.544%   $201.9418   $201.94   $201.95   $201.90  
  Purchase #2 $208.81   11.540%   $232.9067   $232.91   $232.90   $232.90  
  Purchase #3 $214.52   10.437%   $236.9095   $236.91   $236.90   $236.90  
  Purchase #4 $139.96   7.756%   $150.8153   $150.82   $150.80   $150.80  
  Purchase #5 $123.68   8.783%   $134.5428   $134.54   $134.55   $134.50  
  Purchase #6 $237.93   12.262%   $267.105   $267.11   $267.10   $267.10  
  Purchase #7 $15.65   7.826%   $16.8748   $16.87   $16.85   $16.90  
  7 purchase totals = $1,123.23       $1,241.0959   $1,241.10   $1,241.05   $1,241.00