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 $222.35   5.772%   $235.184   $235.18   $235.20   $235.20  
  Purchase #2 $181.66   4.778%   $190.3397   $190.34   $190.35   $190.30  
  Purchase #3 $245.94   4.809%   $257.7673   $257.77   $257.75   $257.80  
  Purchase #4 $213.97   3.114%   $220.633   $220.63   $220.65   $220.60  
  Purchase #5 $209.76   12.209%   $235.3696   $235.37   $235.35   $235.40  
  Purchase #6 $224.61   5.153%   $236.1842   $236.18   $236.20   $236.20  
  Purchase #7 $39.27   3.811%   $40.7666   $40.77   $40.75   $40.80  
  7 purchase totals = $1,337.56       $1,416.2444   $1,416.24   $1,416.25   $1,416.30