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 $215.91   13.843%   $245.7984   $245.80   $245.80   $245.80  
  Purchase #2 $112.50   12.181%   $126.2036   $126.20   $126.20   $126.20  
  Purchase #3 $191.78   7.344%   $205.8643   $205.86   $205.85   $205.90  
  Purchase #4 $248.97   3.594%   $257.918   $257.92   $257.90   $257.90  
  Purchase #5 $213.90   3.374%   $221.117   $221.12   $221.10   $221.10  
  Purchase #6 $200.91   6.404%   $213.7763   $213.78   $213.80   $213.80  
  Purchase #7 $238.46   9.850%   $261.9483   $261.95   $261.95   $261.90  
  7 purchase totals = $1,422.43       $1,532.6259   $1,532.63   $1,532.60   $1,532.60