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 $87.57   8.535%   $95.0441   $95.04   $95.05   $95.00  
  Purchase #2 $210.78   8.749%   $229.2211   $229.22   $229.20   $229.20  
  Purchase #3 $120.76   7.329%   $129.6105   $129.61   $129.60   $129.60  
  Purchase #4 $152.29   8.592%   $165.3748   $165.37   $165.35   $165.40  
  Purchase #5 $133.60   8.860%   $145.437   $145.44   $145.45   $145.40  
  Purchase #6 $11.47   13.264%   $12.9914   $12.99   $13.00   $13.00  
  Purchase #7 $165.73   3.567%   $171.6416   $171.64   $171.65   $171.60  
  7 purchase totals = $882.20       $949.3205   $949.31   $949.30   $949.20