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 $236.55   11.121%   $262.8567   $262.86   $262.85   $262.90  
  Purchase #2 $225.90   7.547%   $242.9487   $242.95   $242.95   $242.90  
  Purchase #3 $212.85   7.638%   $229.1075   $229.11   $229.10   $229.10  
  Purchase #4 $30.93   13.684%   $35.1625   $35.16   $35.15   $35.20  
  Purchase #5 $231.77   11.594%   $258.6414   $258.64   $258.65   $258.60  
  Purchase #6 $216.95   13.576%   $246.4031   $246.40   $246.40   $246.40  
  Purchase #7 $45.80   13.399%   $51.9367   $51.94   $51.95   $51.90  
  7 purchase totals = $1,200.75       $1,327.0566   $1,327.06   $1,327.05   $1,327.00