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 $41.57   4.353%   $43.3795   $43.38   $43.40   $43.40  
  Purchase #2 $92.55   7.759%   $99.731   $99.73   $99.75   $99.70  
  Purchase #3 $77.39   9.793%   $84.9688   $84.97   $84.95   $85.00  
  Purchase #4 $206.88   7.132%   $221.6347   $221.63   $221.65   $221.60  
  Purchase #5 $231.64   13.363%   $262.5941   $262.59   $262.60   $262.60  
  Purchase #6 $237.75   9.791%   $261.0281   $261.03   $261.05   $261.00  
  Purchase #7 $218.91   5.479%   $230.9041   $230.90   $230.90   $230.90  
  7 purchase totals = $1,106.69       $1,204.2403   $1,204.23   $1,204.30   $1,204.20