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 $197.93   6.762%   $211.314   $211.31   $211.30   $211.30  
  Purchase #2 $207.92   7.510%   $223.5348   $223.53   $223.55   $223.50  
  Purchase #3 $10.46   13.735%   $11.8967   $11.90   $11.90   $11.90  
  Purchase #4 $197.51   13.628%   $224.4267   $224.43   $224.45   $224.40  
  Purchase #5 $50.64   3.698%   $52.5127   $52.51   $52.50   $52.50  
  Purchase #6 $206.45   3.520%   $213.717   $213.72   $213.70   $213.70  
  Purchase #7 $84.97   3.201%   $87.6899   $87.69   $87.70   $87.70  
  7 purchase totals = $955.88       $1,025.0918   $1,025.09   $1,025.10   $1,025.00