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 $207.98   13.368%   $235.7828   $235.78   $235.80   $235.80  
  Purchase #2 $242.41   13.532%   $275.2129   $275.21   $275.20   $275.20  
  Purchase #3 $105.66   10.795%   $117.066   $117.07   $117.05   $117.10  
  Purchase #4 $82.89   3.223%   $85.5615   $85.56   $85.55   $85.60  
  Purchase #5 $210.68   3.788%   $218.6606   $218.66   $218.65   $218.70  
  Purchase #6 $25.37   9.653%   $27.819   $27.82   $27.80   $27.80  
  Purchase #7 $138.88   4.243%   $144.7727   $144.77   $144.75   $144.80  
  7 purchase totals = $1,013.87       $1,104.8755   $1,104.87   $1,104.80   $1,105.00