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 $241.69   5.355%   $254.6325   $254.63   $254.65   $254.60  
  Purchase #2 $201.28   5.473%   $212.2961   $212.30   $212.30   $212.30  
  Purchase #3 $139.96   11.475%   $156.0204   $156.02   $156.00   $156.00  
  Purchase #4 $101.37   5.571%   $107.0173   $107.02   $107.00   $107.00  
  Purchase #5 $186.97   3.324%   $193.1849   $193.18   $193.20   $193.20  
  Purchase #6 $10.73   6.570%   $11.435   $11.44   $11.45   $11.40  
  Purchase #7 $19.37   10.858%   $21.4732   $21.47   $21.45   $21.50  
  7 purchase totals = $901.37       $956.0594   $956.06   $956.05   $956.00