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 $118.78   5.766%   $125.6289   $125.63   $125.65   $125.60  
  Purchase #2 $229.34   12.278%   $257.4984   $257.50   $257.50   $257.50  
  Purchase #3 $11.80   12.452%   $13.2693   $13.27   $13.25   $13.30  
  Purchase #4 $219.65   11.709%   $245.3688   $245.37   $245.35   $245.40  
  Purchase #5 $171.78   12.786%   $193.7438   $193.74   $193.75   $193.70  
  Purchase #6 $180.62   13.515%   $205.0308   $205.03   $205.05   $205.00  
  Purchase #7 $235.69   10.511%   $260.4634   $260.46   $260.45   $260.50  
  7 purchase totals = $1,167.66       $1,301.0034   $1,301.00   $1,301.00   $1,301.00