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 $81.57   5.397%   $85.9723   $85.97   $85.95   $86.00  
  Purchase #2 $24.98   5.144%   $26.265   $26.27   $26.25   $26.30  
  Purchase #3 $68.74   9.765%   $75.4525   $75.45   $75.45   $75.50  
  Purchase #4 $186.30   8.401%   $201.9511   $201.95   $201.95   $202.00  
  Purchase #5 $245.92   6.385%   $261.622   $261.62   $261.60   $261.60  
  Purchase #6 $224.51   9.851%   $246.6265   $246.63   $246.65   $246.60  
  Purchase #7 $134.73   13.531%   $152.9603   $152.96   $152.95   $153.00  
  7 purchase totals = $966.75       $1,050.8497   $1,050.85   $1,050.80   $1,051.00