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 $209.87   7.716%   $226.0636   $226.06   $226.05   $226.10  
  Purchase #2 $222.76   7.614%   $239.7209   $239.72   $239.70   $239.70  
  Purchase #3 $230.32   7.386%   $247.3314   $247.33   $247.35   $247.30  
  Purchase #4 $64.29   5.770%   $67.9995   $68.00   $68.00   $68.00  
  Purchase #5 $236.84   12.177%   $265.68   $265.68   $265.70   $265.70  
  Purchase #6 $104.71   5.615%   $110.5895   $110.59   $110.60   $110.60  
  Purchase #7 $26.98   13.219%   $30.5465   $30.55   $30.55   $30.50  
  7 purchase totals = $1,095.77       $1,187.9314   $1,187.93   $1,187.95   $1,187.90