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 $56.26   11.859%   $62.9319   $62.93   $62.95   $62.90  
  Purchase #2 $8.59   8.628%   $9.3311   $9.33   $9.35   $9.30  
  Purchase #3 $7.76   11.631%   $8.6626   $8.66   $8.65   $8.70  
  Purchase #4 $87.57   8.816%   $95.2902   $95.29   $95.30   $95.30  
  Purchase #5 $75.62   13.281%   $85.6631   $85.66   $85.65   $85.70  
  Purchase #6 $161.83   8.277%   $175.2247   $175.22   $175.20   $175.20  
  Purchase #7 $88.51   13.627%   $100.5713   $100.57   $100.55   $100.60  
  7 purchase totals = $486.14       $537.6749   $537.66   $537.65   $537.70