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 $186.33   4.799%   $195.272   $195.27   $195.25   $195.30  
  Purchase #2 $85.96   7.837%   $92.6967   $92.70   $92.70   $92.70  
  Purchase #3 $175.88   5.476%   $185.5112   $185.51   $185.50   $185.50  
  Purchase #4 $195.84   3.869%   $203.417   $203.42   $203.40   $203.40  
  Purchase #5 $207.64   12.604%   $233.8109   $233.81   $233.80   $233.80  
  Purchase #6 $5.84   8.866%   $6.3578   $6.36   $6.35   $6.40  
  Purchase #7 $71.70   9.326%   $78.3867   $78.39   $78.40   $78.40  
  7 purchase totals = $929.19       $995.4523   $995.46   $995.40   $995.50