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 $197.25   10.362%   $217.689   $217.69   $217.70   $217.70  
  Purchase #2 $60.81   10.115%   $66.9609   $66.96   $66.95   $67.00  
  Purchase #3 $238.58   3.140%   $246.0714   $246.07   $246.05   $246.10  
  Purchase #4 $247.84   5.556%   $261.61   $261.61   $261.60   $261.60  
  Purchase #5 $119.94   9.821%   $131.7193   $131.72   $131.70   $131.70  
  Purchase #6 $173.65   4.676%   $181.7699   $181.77   $181.75   $181.80  
  Purchase #7 $74.96   3.693%   $77.7283   $77.73   $77.75   $77.70  
  7 purchase totals = $1,113.03       $1,183.5488   $1,183.55   $1,183.50   $1,183.60