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 $94.81   8.610%   $102.9731   $102.97   $102.95   $103.00  
  Purchase #2 $191.79   5.874%   $203.0557   $203.06   $203.05   $203.10  
  Purchase #3 $216.26   5.289%   $227.698   $227.70   $227.70   $227.70  
  Purchase #4 $143.70   11.526%   $160.2629   $160.26   $160.25   $160.30  
  Purchase #5 $217.82   7.824%   $234.8622   $234.86   $234.85   $234.90  
  Purchase #6 $53.48   13.770%   $60.8442   $60.84   $60.85   $60.80  
  Purchase #7 $40.83   10.463%   $45.102   $45.10   $45.10   $45.10  
  7 purchase totals = $958.69       $1,034.7981   $1,034.79   $1,034.75   $1,034.90