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 $23.44   5.363%   $24.6971   $24.70   $24.70   $24.70  
  Purchase #2 $205.62   12.229%   $230.7653   $230.77   $230.75   $230.80  
  Purchase #3 $164.64   5.588%   $173.8401   $173.84   $173.85   $173.80  
  Purchase #4 $226.44   6.418%   $240.9729   $240.97   $240.95   $241.00  
  Purchase #5 $103.58   5.223%   $108.99   $108.99   $109.00   $109.00  
  Purchase #6 $236.64   10.489%   $261.4612   $261.46   $261.45   $261.50  
  Purchase #7 $148.56   5.747%   $157.0977   $157.10   $157.10   $157.10  
  7 purchase totals = $1,108.92       $1,197.8243   $1,197.83   $1,197.80   $1,197.90