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 $227.60   10.806%   $252.1945   $252.19   $252.20   $252.20  
  Purchase #2 $56.70   8.139%   $61.3148   $61.31   $61.30   $61.30  
  Purchase #3 $61.41   13.692%   $69.8183   $69.82   $69.80   $69.80  
  Purchase #4 $70.25   6.605%   $74.89   $74.89   $74.90   $74.90  
  Purchase #5 $69.68   9.368%   $76.2076   $76.21   $76.20   $76.20  
  Purchase #6 $246.39   7.715%   $265.399   $265.40   $265.40   $265.40  
  Purchase #7 $55.82   11.380%   $62.1723   $62.17   $62.15   $62.20  
  7 purchase totals = $787.85       $861.9965   $861.99   $861.95   $862.00