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 $126.66   7.616%   $136.3064   $136.31   $136.30   $136.30  
  Purchase #2 $131.37   8.371%   $142.367   $142.37   $142.35   $142.40  
  Purchase #3 $162.85   7.267%   $174.6843   $174.68   $174.70   $174.70  
  Purchase #4 $243.54   7.177%   $261.0189   $261.02   $261.00   $261.00  
  Purchase #5 $166.38   8.448%   $180.4358   $180.44   $180.45   $180.40  
  Purchase #6 $180.96   12.728%   $203.9926   $203.99   $204.00   $204.00  
  Purchase #7 $71.69   8.205%   $77.5722   $77.57   $77.55   $77.60  
  7 purchase totals = $1,083.45       $1,176.3772   $1,176.38   $1,176.35   $1,176.40