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 $214.81   5.775%   $227.2153   $227.22   $227.20   $227.20  
  Purchase #2 $213.91   8.783%   $232.6977   $232.70   $232.70   $232.70  
  Purchase #3 $110.87   13.252%   $125.5625   $125.56   $125.55   $125.60  
  Purchase #4 $245.46   5.581%   $259.1591   $259.16   $259.15   $259.20  
  Purchase #5 $242.90   7.114%   $260.1799   $260.18   $260.20   $260.20  
  Purchase #6 $242.60   10.774%   $268.7377   $268.74   $268.75   $268.70  
  Purchase #7 $108.90   10.138%   $119.9403   $119.94   $119.95   $119.90  
  7 purchase totals = $1,379.45       $1,493.4925   $1,493.50   $1,493.50   $1,493.50