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 $52.89   12.487%   $59.4944   $59.49   $59.50   $59.50  
  Purchase #2 $63.96   10.224%   $70.4993   $70.50   $70.50   $70.50  
  Purchase #3 $178.99   4.231%   $186.5631   $186.56   $186.55   $186.60  
  Purchase #4 $197.32   6.641%   $210.424   $210.42   $210.40   $210.40  
  Purchase #5 $95.46   13.306%   $108.1619   $108.16   $108.15   $108.20  
  Purchase #6 $232.85   12.380%   $261.6768   $261.68   $261.70   $261.70  
  Purchase #7 $238.60   11.601%   $266.28   $266.28   $266.30   $266.30  
  7 purchase totals = $1,060.07       $1,163.0995   $1,163.09   $1,163.10   $1,163.20