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 $55.53   11.725%   $62.0409   $62.04   $62.05   $62.00  
  Purchase #2 $47.58   10.446%   $52.5502   $52.55   $52.55   $52.60  
  Purchase #3 $208.36   11.803%   $232.9527   $232.95   $232.95   $233.00  
  Purchase #4 $9.76   4.645%   $10.2134   $10.21   $10.20   $10.20  
  Purchase #5 $32.54   7.448%   $34.9636   $34.96   $34.95   $35.00  
  Purchase #6 $229.42   7.808%   $247.3331   $247.33   $247.35   $247.30  
  Purchase #7 $196.71   8.471%   $213.3733   $213.37   $213.35   $213.40  
  7 purchase totals = $779.90       $853.4272   $853.41   $853.40   $853.50