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 $56.56   11.434%   $63.0271   $63.03   $63.05   $63.00  
  Purchase #2 $83.83   9.823%   $92.0646   $92.06   $92.05   $92.10  
  Purchase #3 $11.43   3.705%   $11.8535   $11.85   $11.85   $11.90  
  Purchase #4 $9.59   13.370%   $10.8722   $10.87   $10.85   $10.90  
  Purchase #5 $243.49   4.512%   $254.4763   $254.48   $254.50   $254.50  
  Purchase #6 $188.36   13.849%   $214.446   $214.45   $214.45   $214.40  
  Purchase #7 $111.33   4.346%   $116.1684   $116.17   $116.15   $116.20  
  7 purchase totals = $704.59       $762.9081   $762.91   $762.90   $763.00